Another check engine light problem

[gwilliams]

All:

Yesterday evening, I experienced one of the lovely check engine light problems. I'm trying to see if I can discover/learn as much as I can about the cause of the problem, before I visit the dealer for diagnosis (Note I have an appointment for this tomorrow, 9/23).

The obvious potential source of the problem is the "gas cap not tight" scenario. After the check engine light came on, I tested the gas cap once I reached my destination, and it seems to be secure. If I turn it at all, it just clicks. (Note also, I always turn the cap until it clicks when I refuel). Interestingly enough, I had refueled the car the day before. However, this was the 8th duty cycle (power up the car - drive somewhere - power down the car) the car had run since refueling. If it truly were the gas cap issue, wouldn't the light illuminate on the first cycle after refueling? After all, that is when the fault should be detected.... (Note, I am trying to rule this out, in case the dealer tries to write it off as such. I am aware of other larger issues causing such a warning light, and want to resolve any problems that may have occurred.)

I have also heard of a service campaign related to such engine lights. I think it is SSC-40D. I cannot, however, find any documentation showing which build dates and/or serial numbers are subject to the campaign. Can anyone point me to such? I'd appreciate it. For the record, my car was built in June 2004 and has a VIN > 90000.

If you know of any other possible causes for such a warning light, I would appreciate it. Knowledge is power, and I would like to arm myself with as much knowledge of the issue as I can before the dreaded trip to the dealer.

Thanks in advance,
Glenn

[DaveG]

It also may have just been bad gas. If you get some gas that has a bit of water in it or something that causes the engine to misfire, it will light up and record a trouble code in the computer.

Best to get the dealer to check it to make sure it's nothing more serious, but there are lots of sensors in the Prius, and lots of stuff that it could detect that wouldn't impair the car's functioning in any way in the short term.

Dave

[wb9tyj]

Mine came on a few days ago...we did the same thing you did...check fuel cap,etc...ended up at dealer...they had to reset the ECU...there was a TSB on this issue......i had tried cycling up and down 15 times...etc...all to no avail...so take it in and let them reset the computer...my VIN >100000, had only 1800 miles on it...built in july2004

[gwilliams]

Well, according to the dealer, mine had code P0136 set. They said per TSB EG038-04 they cleared the light and reprogrammed the engine ECU. All was well for about 3 miles, and now I have a check engine light again. :x :x :x

Anybody have access to the TSBs? If so, could you post a link to EG038-04. I've looked for it with Google and came up with nothing....

Back to the dealer I go tomorrow. Sigh.

Glenn

[gwilliams]

Well, on visit #2 to the dealer, they reported the same MIL code P0136. Stumped, this time they conferred with Toyota support at their California HQ. The story is that they reprogrammed the ECU a second time, with a different "set of parameters". I'm not sure if that is in the referenced TSB or not (I still haven't seen it). However, the MIL (engine light) is now off, and has been since the car was returned to me a few days ago. (He says whilst knocking on wood.)

If anyone can post this TSB (see above thread for the reference number), I would appreciate it.

TIA,
Glenn

[DanMan32]

DTC P0136 OXYGEN SENSOR CIRCUIT MALFUNCTION
(BANK 1 SENSOR 2)

One of the following conditions is met:

Sensor impedance is less than 5 W when ECM presumes the
sensor warmed–up as well as operated normally

Under active air–fuel ratio control, either of (a) and ( is met:
(a) Sensor output voltage is 0.2 V or more
( Sensor output voltage is 0.6 V or less

Under active air–fuel ratio control, either of (a) and ( is met:
(a) Sensor output voltage is 0.25 V or more when OSC is 0.88
g or more and target air–fuel ratio is RICH
( Sensor output voltage is 0.59 V or less when OSC is 0.88 g
or more and target air–fuel ratio is LEAN

Open or short in heated oxygen sensor (bank 1 sensor 2)
circuit

Heated oxygen sensor (bank 1 sensor 2)

Heated oxygen sensor heater (bank 1 sensor 2)

EFI M relay

Have they replaced the oxygen sensor or checked the wiring?

Oh wait, you only have 442 miles on the car. This normally happens for a little while as a coating on exhaust system burns off. I had this too. Went away after a week.

Oh, wait again, that was your last fillup. Lifetime milage 1303. Should have burned off by now.
Check or replace oxygen sensor.

[gwilliams]

DTC P0136 OXYGEN SENSOR CIRCUIT MALFUNCTION
(BANK 1 SENSOR 2)

One of the following conditions is met:

Sensor impedance is less than 5 W when ECM presumes the
sensor warmed–up as well as operated normally

Under active air–fuel ratio control, either of (a) and ( is met:
(a) Sensor output voltage is 0.2 V or more
( Sensor output voltage is 0.6 V or less

Under active air–fuel ratio control, either of (a) and ( is met:
(a) Sensor output voltage is 0.25 V or more when OSC is 0.88
g or more and target air–fuel ratio is RICH
( Sensor output voltage is 0.59 V or less when OSC is 0.88 g
or more and target air–fuel ratio is LEAN

Open or short in heated oxygen sensor (bank 1 sensor 2)
circuit

Heated oxygen sensor (bank 1 sensor 2)

Heated oxygen sensor heater (bank 1 sensor 2)

EFI M relay

Have they replaced the oxygen sensor or checked the wiring?

Oh wait, you only have 442 miles on the car. This normally happens for a little while as a coating on exhaust system burns off. I had this too. Went away after a week.

Oh, wait again, that was your last fillup. Lifetime milage 1303. Should have burned off by now.
Check or replace oxygen sensor.

I was told they checked the O2 sensor, and it was fine...

The Prius tech at the dealership consulted with someone at Toyota's HQ in CA on the fix, the second time around. I'm guessing there may be another TSB in the offering based on my experience. As of this writing, they have not closed out the work order for the second repair (whatever that means). I think I may be a guinea pig for whatever reprogram that was done. Anyway, Toyota corporate is aware of the (in progress?) repair. They have generated a problem log/incident report (or whatever nomenclature Toyota uses for such). I have a problem/tracking number on the work order that Toyota is supposed to follow up on. At least so far, since the second reprogram, it has been trouble free (again knocking on wood).

Thanks for the note and the info.

Glenn