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Q: Check Engine Light on 2000 Toyota Avalon

We took the car to the dealer for CEL, they told us it needed the bank 1 converter replaced. We also took the car to AutoZone and they gave me the printout with same info, but also showed bank 1 O2 sensor could be bad. (I have changed the sensor myself.) We had the bank 1 converter replaced at the dealer and now CEL is on again, dealer says that the computer will not tell them exactly which of the 3 converters is bad so we need to replace the other 2 for an additional $2000. I think something is fishy here!! Seems to me they should be able to troubleshoot the problem rather than just changing parts until CEL goes away because I could do that myself!!
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I am surprised at the response of your dealer. With the dealer scan tool or an oscilloscope the sensors can be monitored to see how they are reacting. Simply put the front sensor should show activity at 2500RPM and the rear should be relatively flat on a catalytic converter that is "good". Cars are getting complex but throwing parts at a car in hopes it "fixes it" is not the right route.
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I'll run through a wiring diagram tomorrow night and see where things tie in that could cause all these problems. I am surprised I work primarily on Lexus/Toyota and the dealer network is great, the information Toyota dealers have access to is also brilliant.
Will respond tomorrow.
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I was looking at a wiring diagram. It seems likely that the failure of the cruise control, wipers, and horn were caused by a problem with wiring in the area of the steering column. I haven't seen this as a common problem on the Avalon. Has someone fitted an aftermarket alarm or remote starter?
The fuses for each circuit do over lap.
Drivers door mirror switch 5Amp (ECU-ACC)
If you have seat memory that includes activation of the mirrors fuses in that circuit are 7.5Amp (ECU-B fuse), 10 Amp (gauge fuse), and 30 Amp (power seat fuse).
Horn 10Amp (fuse marked horn)
Cruise Control (three fuses, 10Amp (ECU-IGN), 5Amp (ECU-ACC), and a 10 Amp (fuse marked Gauge).
Wipers and washer circuit are protected by the same 25 Amp (fuse marked wiper).
So there is some over lap on the fuses. But I can't explain having wiper motor troubles so soon after the wiring had been replaced and the fuse replaced.
Thanks for the reply, autotechpat! I also called a reputable repair shop that we had previous used on another car and they confirmed your answer. So, I am now taking it to them Thursday morning for evaluation. And to further confirm, I had a family member call a tech in their area, he also agreed.
Maybe I should have also mentioned that we are having electrical problems too. Wife was adjusting drivers rear view mirror and it stopped working, along with the horn, and the cruise. I check all of the fuses that referenced any of these and could not find any bad fuses. (I did not troubleshoot relays however.) Here's the good part. After I was done checking fuses, wife drives car to work and turns wipers on, they stopped parking. Took to dealer for diagnosis along with a noise in steering column. They said harness under airbag was cause of noise; horn, cruise and mirror was a fuse; wiper park problem was caused by wiper switch shorting out and frying park portion of moter. Result: wiper switch, wiper motor, wiring harness and fuses were replaced for a mere $1000! 2 weeks later the wiper motor totally froze up, had to be replaced again. Dealer says they have no idea what is causing these electrical problems. It is getting more and more obvious to me that this dealer does not have any quality techs. But they have been in this town for 30+ years! Not sure how.
To: autotechpat, No there are not any aftermarket accessories. And thanks for the fuse info, that will help me considerably in the future. We have an appt this am with the shop I had called Monday, so we'll see what they say about this. Wish me luck!!
Took to dealer yesterday after getting diagnosis from independent shop showing downstream cat was the 'bad' converter. Dealer says Toyota tells them that all converters must be replaced when code P0420 is received. Dealer paperwork from previous diagnosis stated that "P0420-catalyst below threshold. This model does not give code P0430 for bank 2 will only give code P0420". Yesterday they said that it was still showing same code, even though they originally agreed to troubleshoot further in order to pinpoint actual bad converter. They eventually agreed to replace only the downstream cat and put bank 1 cat back on for difference in cost of converters and waive labor. I am still not happy with answer. Only took car back to dealer to give them a chance to make this right.
Last night on our way home from shopping, the CEL went out. My wife stated that all of the lights on the dash "were lighting up now" as she started the car. I asked her what she meant and she said they weren't coming on before. As far as I know, all of the dash lights come on at startup as a system check, right? Something is weird here. I am now wondering if all of this is electrical in nature and that the converters are not really bad. She also told me that she had gotten gas the day before the CEL came on this last time. (She can not get the gas cap very tight due to her arthritis.) The printout I obtained from AutoZone also showed a code P0440 in addition to the P0420.
What brand of sensor did you use, Some vehicles have a problem with aftermarket sensors so its always best to use toyota brand sensors just to make sure the universal sensor isn't giving you a false reading.
get another estimate maybe try a Napa autocare center I see quite a few close to you they have ASE certified installers and carry their own parts.
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