A little history....

Car had a loose battery terminal and the lights started flickering and the engine ran rough.

Have a Maxscan GS500 so I can read and erase codes.

Fixed the battery terminal issue and the service engine light came on and the idle was surging up and down in a cyclical fashion.

Read the codes...P0122 Low TPS voltage, P0171 system too lean bank one. Also had an O2 sensor code (can't remember the number).

So I purchased a new O2 sensor....changed the upstream sensor near the radiator and that code didn't reset after I cleared all codes, the TPS code was still there and the check engine light reset.

So I changed the TPS.....no change, after code erase, TPS low voltage code came back.

So I tried pulling the battery terminal and putting it back on and then driving the vehicle to relearn the PCM fuel trim.....same code still showing P0122.

Put the old TPS back in.

Looked at my service manuals. Went through the P0122 service check procedure. Checked ohms on the TPS, OK. Checked voltage on connector after removal with key in on position. Voltage OK. Then took PCM out and backprobed connector with Ohm meter to verify connection back to TPS. Both check out. Only one left was to check connector A28 which is a gang connector. Took awhile to get to it in the wire loom under the fuse box. Pulled each of the three connector bars apart and tey wrere all gooped up real good with white dielectric grease....assume they were OK.

Still have the code and surging idle!

Any advise would be helpfull because only other item in the service procedure is to change out the PCM

 

Xxxxxxx

 

One other thing.

Seems the SES light is flickering, not just on.

Wonder if this confirms the PCM is sick ?

 

Whats the Voltage at the battery ??? I'm wondering if the battery is weak , I'd have te charging system/battery checked to confirn they are proper ... especially the light flickering might be indicating a weak battery/alternator

 

engine off 12.4V

engine on 14.5V

Both at battery terminals.

So tonight I decided to check again.

Started and cold it had a rough idle...missing somewhat.

Read codes and still had the P0122 with SES on and somewhat flickering.

Erased all codes....threw no new codes.

Idling at 1,800 to 2,000 rpm.

Decided to look at data stream. Noted IAT was at between 102 to 111F, seems high since outdoor temp is around 64F and engine was only running for 10 minutes if that long...maybe problem is intake air sensor?

I think I'll check the IAT tomorrow morning with engine cold to check...

Possible codes not yet set indicate P0174 right bank lean.

Any clues?

 

So I sprang for a rebuilt PCM on Ebay for $120 w/free shipping....ecuexchange.com

Should get it next week.

Before I decided to purchase this I disconnected the alternator cable and I still had the racing idle problem, but the ses light was on steady and not pulsing.

I'm also going to change out the IAC and also the rear upper O2 sensor near the firewall.

So I hope when I put in the new PCM everything works OK.

We'll see

 

Xxxxx

 

So Saturday I put in new plug wires, distributo rotor and cap and a new EGR assembly while I had the intake maifold off so I could change the rear O2 sensor. Also put in a new intake manifold gasket and new IAC servo.

The new PCM was also installed.

Started her up and drove about 5 miles to reset the IAC.

3 miles and the SES light comes on.

Also, lights are still pulsing, and the idle is still somewhat unsteady.....

1 Code present...you guessed it P0122 low TPS voltage again!

I ordered a rebuilt alternator................

 

So my daughter has been driving the car around town, and yesterday the battery light comes on.....thought it was the alternator!

Rebuilt has arrived via UPS so I'll change it on Saturday.

I'll keep you all posted.

 

Hmmm sounds like I was right with the alternator/charging system check ... might have saved you big $$$