mzeitlin

I have a 2000 ES300 with 96,000 miles on it.
A few days ago trouble code 1150 popped up (following a check when the check engine light activated).
I cleared it expecting to duplicate it next time I started the car. It did not duplicate.

Next time, 3 codes popped up:
1125
1130
1135 ...

I cleared those in the hope that I would get consistent errors. They did not duplicate.

The next I started the car - nothing during the run time.

Any thoughts on to what may be happening? Are these codes related (especially 1125 : Throttle Control Motor Circuit Malfunction)

The car is running fine - I notice no change in performance.

mzeitlin

I checked the front o2 sensor and it checks fine (heater coil shows normal resistance).
I cleared the ECU and re-started the car and now I have a new trouble code ... P0171 (mass air flow sensor).
The other codes don't show up (after 10 minutes run time).

Could the MAF be causing all of this?

Hayk

iTrader: (1)

After clearing the codes, has the car only been running for 10 minutes?

Sometimes random codes could come from an poor voltage supply to the computer. This can be caused by wiring problems and/or a bad alternator and/or battery.

mzeitlin

I think the problem(s) is solved. I cleaned the mass air flow sensor and control wire contacts. The car ran fine before, but does seem to be a bit smoother after I did this.
I cleared the ECU and no more trouble codes have appeared (10 - 20 minutes run time). I suspect it was intermittent wire connection and perhaps a dirty MAF sensor. Seems to be fine for now.

(I am so glad I didn't have to replace Bank1 Sensor1 Oxygen sensor !! - at least not yet)

mzeitlin

Turns out the problem was cylinder 1 direct coil (cop) failed. I ended up replacing the bank1 sensor 1 oxygen sensor anyway since it was original. Strange sequence of trouble codes had me all over the place (mass flow, sensors, etc.). But one code that popped up was cylinder 1 misfire and then went away when the other codes showed up. I checked the spark plug in cylinder 1 and it was black as can be where the others were fine - so clearly it wasn't firing.

After installing the new coil, performance jumped - especially in how the transmission shifts (smooth).

The coil problem must have been intermittent because it was barely noticeable even after the check engine light came on.

It's nice to have the car running great again. We'll see if the trouble codes stay cleared over the next few days.

mzeitlin

Well...trouble code trouble continues ... all previou clodes cleared except now I have P0171 coming on.
Seems the mass air flow sensor needs replacing. I cleaned it and it looks "new", but the code keeps coming back.
I'll replace it since this one is 16 years old and see if this resolves all of my trouble codes.

(What causes MAF sensor to go bad if it's not dirt buildup related?)

mmatheny

The wire in a MAF heats up to a certain temperature. Like anything giving off heat, any air passing over it reduces the temperature (wind chill!) - the resistance changes with the temperature of the wire and that is how the ECU computes the air flow. Maybe the resistance is not in spec being so old.