Technical Topics


This page is designed for the problems that are happening now and in the recent past. We all see different problems before others, for whatever reason. This page is just for us, since sometimes even Toyota does not know the answer, or that we are seeing these things first.

P0420 Code Coming back after the repair. From time to time you will or have had this happen. You did everything right - Scanned the system - got the snapshot - read the snapshot - came to the conclusion that the cat was not working. You ordered the cat (if there are two then both need to be replaced) the parts came in and the install went as planned. You road tested the vehicle and watching the scan tool were satisfied with the results. This is the good part of the story.

Now several days later you get the vehicle back with the same P0420 code. You check your work and sure enough the rear O2 sensor is saying that the convertor is not working. This is where you need to focus on the situation. The chances of the new convertor (s) being bad is almost impossible, so what went wrong. Here is a snapshot of a good Cat and O2 sensor for a 99 4Runner with Cal specs. The A/F sensor has activity and the O2 sensor has a very tight pattern, but not flat. Most of you know the best way to check the system is to drive in 2nd gear then go to full throttle then back off quickly. This will give you the A/F sensor activity ( full rich 2.0 volts) and the O2 sensor reaction (full lean 4.9 volts). If you don't get this picture, or those voltages what is wrong.

We battled this and with the help of the tech line were told that if the O2 sensor was getting too large a wave pattern then look for a leak before the O2 sensor. It may be where you connected the cats or the O2 sensor. We found that even a small leak, the didn't make any sound, would allow oxygen into the system and that introduction of oxygen would send the O2 sensor crazy. Our culprit was at the front pipe, there was some rust that was not cleaned before the cat was bolted up and it was enough to trip the code when the engine decelled. We cleaned the surface and it corrected the problem. The exhaust did not make any noise. We had to confirm or trust that the replacement parts were good and working, and that our work in installing the new parts was the weak link.

P0300 code - Random misfire condition. We are seeing more of this than in the past. At first we felt that sometimes the type or quality of the fuel being used. We tend to educate the customer and offer some suggestions as to the reasoning for our suggestions. We noticed that when the scan tool is used to check the code the freeze frame shows that the condition was noticed within the first minute of cold start up. In getting more information, since we do not like just the gas answer, we discovered that the system remembers the last shut down and if it was running rich or lean at that time, it is looking for that as a continuation at start up (the software needs to be changed so that it starts fresh without any memory as to rich or lean at shut down). Then we found out that in the freeze frame there is a negative value at "Short F + #1". The system is looking for something less than -4% to a positive ( this -4% is an floating value but used as a reference by the Gods in Torrence). If this is present and then if you take off the purge valve hose at the intake manifold the reading should go to positive. If that happens then the canister is probably contaminated with fuel from the owner over filling the vehicle at gas up. The only way to resolve this is to replace the canister and educate the owner about not over filling the fuel tank. Fuel contamination is still an issue so adding some isopropal dry gas to the gas tank and check the measurement of the Short F+ when the new canister is installed.

01 Solara with a check engine light and performance problems. The last few days have been very interesting for me with the aforementioned Solara 1MZFE.

Day (1) mil on: misfire code for cyls 1-4.Swap coil pack with cyl 2-5 ,clear codes,road test.Code set for cyl 2-5.R&R faulty coil pack and take car on two 15mi road tests with time between,no hard codes or pending codes. Release to cust.

Day (2)back with mil on :code for o2 B1,S2.Bad o2 confirmed.R&R o2,take car on same test ride circuit(3 times),no pending codes.Release to cust.
Day (3)God hates me.back with mil on:Codes for o2 again plus two trans codes,lock up solenoid and accumulator.Unable to verify any problems in these areas.Instructed by district rep to replace ECM because of the random codes.R&R ECM,go on test ride circuit again,no codes set,hold overnight.

Day (4)Take car on a 3rd test ride circuit and same codes reset with mil on again.While checking with scan tool-noticed a faint flickering in the mil? Went for test ride to do active test for lock-up sol to see if it was functioning,no problems. On way back to shop flickering of mil became more noticable.Took off from traffic light and mil went off and car died on me.This is the kindest thing that could happen,now I have something solid !

Tow back to shop: Trouble-shoot mil that will not go on.With another tech in car watching dash,I check underhood area for loose connections.While gently squeezing engine harness near right shock tower, mil comes on ! Evidently there is an internal break in the harness caused by engine torque flexing the harness.

Upon leaving work today,harness was pulled through into engine compartment and opened up to attempt repair.Hopefully I'll find the bad wire on Sat morning.Knowing my luck,I won't be able to find it and I'll have to put an engine harness in it which is the last thing I want to do.

Hope you had a better week Jack :)Hopefully you can gain something through my misery.BTW,if you have a chance check my web site at enjoy. 4/16/02

00 Sienna check engine light coming on and going off. You are probably starting to see this condition on the Sienna's you have just delivered. We have seen 3 and I have had questions on several more. You will get a code of P0770 for a trans SL valve. The Toyota repair gods think they have found the problem. Its the torque convertor. We have one on order and will know more around 7/20. There is no problem with driving the vehicle since it does go into OD but not just as fast as it is designed to and the code blows. 7/13/00

00 Avalon wind noise. We have been getting customers coming back with the complaint of wind noise. Since we dealt with the early Avalon models and in general the Toyota product does not have this condition we tried to see if we could help. In trying to quiet the slight wind noise we were unable to do much then we drove several others (new on the lot) and found that they also made the same noise. You won't get them all back since the radio is enough to cover the noise level but if you get that 10% customer you may want to take them for a ride in another Avalon. We think that the mirrors are the cause but Toyota has not heard of this condition. 5/00 Update: Toyota has sent us some improved front door window seals that are fatter and do the trick. The ones we have installed have corrected the condition. These do not have a part number as of yet but the famous TSB should be out soon. 7/00.

Brake Clicking when changing direction. We are seeing more and more of this condition (lately the Sienna has been the vehicle du jour). Toyota does not officially recommend this but if you order a front brake hardware kit and use the flat pad shims only and add these to the brake pads the condition goes away, warranty pays for the repair. 4/00

Sienna transmission. There aren't many out there that are failing, contrary to popular opinion or some net sites, but here are some of the 2000 ones have had some problems. I don't have enough information but several problems have been reported. 2/00. Update: 4/00 the reports of more problems are still coming in, again it seems that the ones affected are happening after long drives like vacations.

Check engine light P0441. This code is becoming more common. It seems to be just Camry's and Tacoma's. You may not be able to duplicate this condition but after several tries you will be convinced. My advice is to read the code and replace the canister since the small valve is blocked from whatever is breaking up inside. We are starting to see some failures with new canisters after several months. You may want to check for how the hoses fit the canister, you may find that some don't fit very tight and a clamp is needed. Note: automatic trans. and standard canisters are different.

Check engine light P0440. This code is fairly common and is caused almost always by leaving the gas cap loose or off during refueling if the engine is running. Normally just checking for the cap and talking to the customer will correct the condition. In later models other reasons can cause the same code so if the cap is tight and the customer has been "schooled in gas cap 101" then you may have to look at loose fitting hoses or some other cause.

Camry brake noise. In 97 we started to hear customers complain of brake noise similar to ABS sounds at the end of a stop. After driving the vehicle with the customer we noticed that it only took place after the brakes got "hot" and at the end of a stop, even at 30 MPH. Toyota tells us the problem is most likely only with 4 Cyl Camry's with steel wheels. We now have an upgrade kit available that seems to be working. In march of 99 we have a new bulletin that seems to say that all is not well with the 97-99 Camry and Avalon brake noise. New pads are out there but we have not has to use these yet. Update: The new pads along with the update kit seems to work, we have not had any comebacks since the kits were installed on the customers that complained of the brake noise. 6/99

Convertor failures. We have seen more check engine lights for catalytic convertor failures. They seem to be 4X2 Tacoma's and some RAV4's. No other cause is found and replacing the convertor corrects the condition. I'm only mentioned this to save some time and a come back for the customer. 3/99

IAC valves. By now you have replaced many of these. They seem to be the 95 to 96 4 Cyl Camry's and RAV 4's and only affect the cold start feature. Toyota says that carbon from inside the breather system is the cause and restricts the IAC. Replacement of just the valve corrects the cold start problem. Cleaning is now possible see below. 9/98

TPS for Tacoma. We are starting to see failures with the TPS for 4 Cyl Tacoma's. Normally the customer will come in with a check engine light on, you read the code and scan the switch for proper operation. All is normal so you release the vehicle back to the customer "saying it just happened and let us know". You can be a hero if you just replace the TPS or go on a 30 minute road test and I think you'll find it will come on for you. If you question the customer further and ask if they notice a hesitation sometimes this will help confirm the TPS failure. 6/98

Cam belt tensioner. We are starting to see more tensioners sticking on the 1MZ-FE engine. Normal this is noticed when the timing belt is replaced and you can't get the proper tension. Remove the tensioner and clean and lube the pin to correct, going back to parts for the correct belt will not help. 10/98

TRAC light on. If you have a situation to have a Camry or Avalon come in with a TRAC light flashing and ABS light on don't panic. If you are normal, you will go for the TRAC light as the cause and with using the scan tool you'll get a DTC 43 code. Ignore this and pull the short pin in the check connector and find out what is wrong is the ABS system. Once you fix the ABS problem the TRAC light will go out. 9/98

IAC cleaning is possible. As more of the Camry's and Ravs go off warranty the valve is still causing the cold start problem. I was told by a tech that they have been cleaning the valves for several months without any comebacks. Its fairly easy, you need to get a used wiring harness or make your own I have even used the harness from an 90 Camry or any model with an IAC. Get a valve out of parts (the warranty bin should have several) and test your wire leads and by using a battery power the valve and see what contacts open the valve (one side opens and one closes the valve). You want the open direction. Now the next time you get one in take the hose off the throttle body and have some good carb cleaner, connect your leads to the IAC valve. Start the motor (it helps to have a friend keep it running) and spray into the square opening on the side of the throttle body while cycling the IAC valve off the battery, you must spray into the square hole, the motor will try to stall. At first nothing happens then you will hear an increase in air flow then an increase in engine speed. That's it. When you are done you will have to reset the engine light, I remove the EFI fuse for 15 sec. Thanks to Dan Root for the tip. 3/99. Its even easier if you just loosen the connection to the IAC and with someone controlling the Throttle you can just connect and disconnect the plug while spraying in the IAC port. 1/22

Clutch pedal bracket T-100. Most of you have seen the clutch bracket crack. Most customers come in saying that the clutch needs replacing. This seems to be earlier models but unless its been changed it will be happening for some time. I have no real easy way to replace the bracket except don't have your biggest tech do the repair. 8/98

99 RAV with no start or really delayed start. We had a RAV with a no start condition and codes of P0340 which is saying that the cam positioner sensor was out of spec. We replaced the sensor and the same thing happens. We tested the circuit and followed ideas from the Tech line. To make a long story short we replaced the Computer and it solved the problem. The motor acted as if the timing was really off, it would tend to lock up at times then just turn over. 2/99

97-00 Camry parking or headlights staying on. We have found several vehicles with this condition. After thinking that the switch must have been the cause we found that the tail light relay part # 90987-02012 was the cause. We have replaced these and have had no problems. They are a little tough to get at up under the dash. 6/98. I have also encountered headlights staying on with the key out of the ignition. They may go out when you open the door (new option?), the cause has been the integration relay for Camry's w/o daytime running lights and the daytime running light relay for those with daytime running lights. 12/99

Cruise Control will not upshift into OD after downshifting. We started to see this happening in 97 with the 4 Cyl. 4 Runners then other models. The Corolla was solved with the new cruise computer but it is happening on others. Doing some research I have found that there is a circuit that comes from the ECM to the cruise control ECU. The circuit is labeled OD1 on the ECM and terminal 14 on most cruise computers. The interesting thing is that I don't know exactly what that circuit does but it solves the shifting problem and does not affect anything else. All models have this circuit except the Runner and Tacoma. 2/99 Toyota has come out with a service bulletin on this and the cruise control ECU's the cause so consult the bulletin for the parts you may need. 4/00

96 Avalon code P0770 overdrive solenoid. We are starting to see a failure rate on the overdrive solenoid for the trans. At first you may want to replace the solenoid but you may find that as in the past these don't fail offer. Then you will talk to the Tech line and they will say that they have some dealers replace the valve body to solve the condition. What is really happening is that you, upon inspection of the fluid of debris in the trans. oil pan will find that there is some sludge or abnormal build up. My suggestion is to flush the transmission and clean the pan and filter. We have the advantage of a transmission flushing machine that does a pretty good job. It seems that the valve body is very sensitive to debris and will cause the check engine light to come on when the trans is shifting fine and the only reason that the customer came in is because of the light. We are working on one now 4/99 and have replaced the valve body and flushed the fluid, after 2 days of driving the light came back on . We are going to have the customer drive the vehicle for several days, clear the code and have them drive some more. Stay tuned for more. 4/99

95 4Runner V6 with electrical problem. I have seen a common problem that has eluded me in finding the actual cause. Customers will complain that at times or many times when stepping on the brake the radio will cut out and the lights may dim then return to normal. Some have had the engine stall, which creates and I agree a safety problem. I have been able to duplicate the condition on some models. Until recently the Tech line has chose to ignore the condition but it turns out that the Lexus line has had the same problem. The funny thing is that only the 95 4Runner Limited with the 3.0 and loaded model is affected. I always knew that a ground somewhere was the cause. They are saying that cleaning the negative battery cable at the battery and to ground from the battery is needed (clean down the paint where it bolts to the vehicle). Add a ground wire from the negative battery connection to the inner fender. 4/99. Update: Still some sensitivity with the load showing up when the radio cuts out for an instant then comes right back on. Ground improved the general running but the problem is not totally eliminated but greatly reduced. 6/99 More updates from Pat in Atlanta: On the 95 4Runner with electrical problems topic, I have fixed many of these vehicles by increasing the size of the power feed from the battery to the main slow blow fuse. It seems that the wire heats up and causes a voltage drop in the system sometimes causing the EFI system to shut down. Thanks Pat 5/00

96 Tacoma 4 cylinder with auto trans. Vibration. The 96 Tacoma 4 cylinder has a problem in drive since the idle speed is so low and cannot be adjusted. Toyota has finally certified the upgrade of he ECM to raise the idle speed about 70 RPM which helps. The part number is the same as the one on the computer but change the last number to 1 or add 1 to the last. 3/99

Tacoma drive shaft noise. The Tacoma has a small problem with the drive shaft in that it makes strange noises when something inside the shaft separates. It may be a ringing noise, a snapping noise or a noise like a loose heat shield or a loose baffle in the muffler or convertor. If you come across this it is probably the shaft. 6/98

Vehicle will not take gas from pump. This is becoming more common. I have seen it on Corollas and Camry's. In each case it the purge valve on the canister assembly that is causing the problem. Order the canister assembly and the purge valve will come with the unit. 8/98

98-99 Camry's with noise over bumps. This is not really new but still unsolved. Toyota as of 4/99 is still working on this problem. Some customers don't notice the noise from the front or it takes a certain type of use, driving habits or even temperature, since we are far down the feeding chain for information I really don't know. We have installed some of the strut bumpers and they have helped. The noise from the rear is easier to correct. They seem to be the ones produced in the states so if you find the noise unusual installing Japan spec rear struts it works. In talking to the Tech line some dealers have tried 6 cyl. struts and keeping the springs the same but we tried and it did not work. 4/99 Update: Toyota is working with the manufacturer of the struts made for the US built Camry's. The strut company is owned by a European company that feels that the looseness or dampening for the first 1" of travel is desirable. We know that our customer are not as sure as they are, but the strut company is being stubborn. 7/99

Update: The new upper mounts are available from Toyota in sufficient quantities and seem to be working. 2/00

Corolla wheel bearings. If you get a Corolla in that hit something with the front or rear suspension that damaged the strut make sure that you replace the wheel bearing. It may seem fine now but it will probably come back with a noise and the bearing will be the cause. 4/98

Tacoma will not upshift. We started seeing several Tacoma's with no upshift complaint. You could do it manually but it would not go up gear in Drive. Normally you will get a code of P1780. We found that the neutral start switch is the cause. Replace the switch and it corrects the problem. 3/99

88-91 Camry's poor running. I know that this may seem like an old topic to cover but its becoming current. Lately we have had 6-10 Camry's of this year range come in with the same poor performance complaint or an intermittent no start. We did the normal testing based on experience and found that in a majority of the cases the air flow meter was sticking or failing. We are able to locate good used ones to save the customer the $550 for a new one but that supply will probably end. 4/99

97-99 Camry front window coming out of track. This really has been a problem since the body change in 97 but at first we all thought that the cause was something contacting the left outside mirror. Now Toyota has made the window glass thicker without increasing the runner or seal gaps. If you have a Camry come in, and you will, with the front window out of the track and the front runner bent follow these instructions to correct it from happening again. We found this out about 2 years ago and it works. Straighten the front runner or replace it if you want but it may be on back order for some time. 4/99 Update: I have tried the fix of adding spacers but they don't work and we have had to reposition the window on more than one case. Its a nice idea but the repositioning is 99% effective.

99 Corolla and Solara fuel injector problems. The 99 Corolla fuel injectors have a problem that causes a severe misfire. It is a bad "batch" labeled 828. This is engraved on the injector and if the numbers next to that is between 05 to 25 you will need to replace the injectors. The bad news is that the parts are on intergalactic back order. Most of the models affected were built between Aug -Nov 98. The problem is that the laser welds on the pintle is breaking off and causing the problem. If you use a scan tool you will get a misfire code for one of the cylinders. Toyota has removed all the ones from stock by now so the new ones are good to use. The Camry is not affected as of yet. 6/99. Now the whole story is coming out and any 99 model may be affected if it has the Denso brand injectors, the replacement Nippon Denso are fine. 8/15

97-99 Avalon temperature control problems. The Avalon XLS with auto temp control is having a failure of the a/c amplifier. It also controls the ambient air temp. gauge so if a customer comes in and says that the fan does not work and the temp. gauge is blank its the amplifier. We started seeing this in 3/99 and more have happened. The part is on backorder now. 6/99

97-99 Camry and Solara rear wheel bearings. We are starting to see some noise problems with the rear wheel bearings on these models. It seems to be also limited to the right rear side. You will know if you have this if a customer come in mentioning that they hear a "roar from the rear" at some speeds say between 30 - 65 mph. It is different on each vehicle and the noise does go away at some speeds. When I heard this I thought that it sounded like snow tires or tires that have worn edges (think 90 Corolla and Goodyear tires). We replaced the right rear wheel bearing and the noise still was there with the new bearing. In desperation we took a 99 Camry from stock and installed the right rear bearing from it and the noise stopped. The new bearing we installed felt "loose" compared to the OEM one. Toyota is aware of the problem and is working with the manufacturer. The cause seems to come from some impact, say a curb, which damages the bearing race just a little and then the noise starts at a later date. 7/99

Sienna rear washer dripping. It turns out that the spout was changed for the rear washer in the late 99 and early 00 model Sienna's. In doing so they now realize that the fluid may dribble out when warm weather heats the fluid in the line that runs along the roof or just be pulled out while driving.
It does make a mess and the white reside is unsightly but they have a fix.
They are now installing the new spout on production vehicles and will have the redesigned part available around Oct. 1, 99.
If you want to stop the dribbling fluid then you can go back to the washer bottle area and take out the check valve and join the two hoses together with small plastic tubing, we would use a vacuum connector. This will stop the dripping but will take the pump longer to provide the fluid to the rear window. 8/13

RAV 4 and the X05 update. We are starting to see these come in and as things will have it the first two needed the transmission. What we did find is that you can know before hand how far you will need to go, if you take out the drain plug for the differential. The plug is metallic and when the washers let go it sends metal everywhere in the transmission. The ones we took apart to inspect showed us that if we look at the drain plug, for the transmissions in the number range, we will know if the transmissions will need only the washers or the unit. I know that Toyota did not mention this in the instructions but since you can only do one at a time, since we only have one engine support bar, it really helps to know how long the vehicle will be tied up. 8/16

98 Corolla squeaking from the right front. We are starting to see more of this complaint on the 98 Corollas. We have found that the right inner tie rod end is the cause. I can't say what in the joint is the cause but you will hear the noise mostly at low speeds even in your parking lot, it may take about 5 minutes of driving to hear it. You can even bounce on the right fender in the shop and hear the same noise without the wheels turning. I took off the outer tie rod end and could feel the binding in the inner joint. Since the part is on backorder more of you feel the same thing. At least its not the Goodyear tire problem. 8/23/99

Air Flow sensor removal problems. If you have not had a problem with removal of the Air Flow sensor on an 99 Camry yet you may find that the threads will come out with the sensor. You did not do anything wrong but Toyota did something different when the were installed.

Sienna head gasket leaking. Got an e-mail from Long Island and he tells me that they are seeing some 99-00 Sienna's that are reporting coolant loss and replacing the head gaskets corrects the condition. Nothing official yet but Toyota is working on it. 12/18/99

00 Celica standard transmission. Its been reported that the standard transmission Celica is having a trouble handling the 6th to 3rd gear shift and complete failure (to put it mildly) can occur. Nothing official yet just a verbal update. 12/18/99

Whine from engine on 2.7 engines. If you come across a whine from the engine and you swear that its the water pump you may want to check for an alternator failure. We have been fooled into thinking the water pump is the cause then we have to tell the customer that we were wrong and the alternator is the fault. To add to the mix of guessing is the clutch fan makes the same type noise so taking off the fan belt may not be as accurate as you think since the fan is belt driven. 4/00