PO131 code

[GPFred]

Ok, I need to pick a few brains. I have a 00' GP SE with a 3.1. History is I have replaced the front oxygen sensor and CAT, 2 of the coils, spark plugs and wires (OEM). The intake had a history of leaking at the front, but was stopped by some kind of stop-leak. Coolant level is fine and has remained so, even after a fix of the coolant level sensor (i.e. cleaned out). Now, I have the PO131 code on the front sensor again. The car starts fine, runs good at even speeds, gets about 20MPG around town and 25MPG highway. But when it comes time to tromp on it, it feels like it is fighting and holding back, and if I ease off the accelerator the power picks up, almost like its getting too much gas. Transmission shifts fine thru all gears at normal acceleration, but seems to want to not downshift on heavy acceleration. Its almost like something has been slapped over the tail pipe at the time of heavy acceleration. Any help would be much appreciated. I am planning on taking the car back to place that did the CAT replacement.

[GTP Dad]

You may have an injector problem. You didn't say how many miles you have on the engine but it is possible that the injectors are going bad, especially since you say that when you hit the gas is seems like something is clogging the exhaust. I would have the resistance on the injectors checked to see if they are within spec. Also check the TPS to see if the voltages are within normal ranges.

It is possible that the cat is going bad but doubtful since most of them will last 80K miles or more without any problems. However, if too much gas it getting into the system then it could have damaged it. It is worth having it looked at.

[GPFred]

Thanks GTP Dad, I din't think about the injectors. But wouldn't they throw up a code if they were going bad. ALso, what is the TPS? The engine has just over 86K on it and the CAT was replaced just 2 months ago. I'll try an injector cleaner as well. Of course if the injectors are bad, cleaning may not help. Thanks again.

[GPFred]

GTP Dad, I checked the Throttle Position ( I believe thats what I checked) sensor and was getting a low reading of less than a volt from it while plugged in and the engine running. I then checked the signal from the PCM at the plug for the TPS and was getting the requesite 5 volts. Just not sure if I did it right according to the book. Any help would be appreciated. If I did it right, then I believe the TPS is shot, but wouldn't it give off a code indicating such?

[BNaylor]

Originally Posted by GPFred

GTP Dad, I checked the Throttle Position ( I believe thats what I checked) sensor and was getting a low reading of less than a volt from it while plugged in and the engine running. I then checked the signal from the PCM at the plug for the TPS and was getting the requesite 5 volts. Just not sure if I did it right according to the book. Any help would be appreciated. If I did it right, then I believe the TPS is shot, but wouldn't it give off a code indicating such?

The PCM feeds a reference voltage of 5 volts to the TPS. At idle the reading with a voltmeter will be around .5 volts. It will increase as the throttle angle increases to a maximum of approx. 4 volts at wide open throttle.

If the TPS voltage is less than .16 volts you should get a DTC error code and the same if greater than 4.71 volts.

Therefore, if the TPS voltages at idle read .5 volts and increases according depending on throttle position you can probably assume the TPS is OK.




Thrasher CAI, DHP v1.0 PCM,
3.25 SC pulley, CAIT GMAF, Hi-Flow CAT,
u-bend delete, 160 TS, ZZP Stage 1 TB,
TB spacer, MSD 8.5mm wires, Autolite 104s,
Goodyear Gatorback Serp. & SC Belt,
Nitto NT555R Drag Radials

[GPFred]

Therefore, if the TPS voltages at idle read .5 volts and increases according depending on throttle position you can probably assume the TPS is OK.

Thanks. Then based on the fact that the TPS reading did not change with throttle increase, then its probably bad. The reading was definitely above .5 volts, but did not increase with throttle increase. Appreciate the help. Guess I'll be picking up a new TPS on Monday.

[BNaylor]

No problem GPFred. GTP Dad is the one who suggested checking the TPS. I was just filling in the blanks and providing the voltages and parameters. Good luck and let us know how it turns out.



Thrasher CAI, DHP v1.0 PCM,
3.25 SC pulley, CAIT GMAF, Hi-Flow CAT,
u-bend delete, 160 TS, ZZP Stage 1 TB,
TB spacer, MSD 8.5mm wires, Autolite 104s,
Goodyear Gatorback Serp. & SC Belt,
Nitto NT555R Drag Radials

[GPFred]

Well, I took it in for a complete engine diagnostic and the TPS is fine, however, the %$**@# front O2 sensor is intermittent. It was brand new a couple of months back, so I am taking it in tomorrow to have a new one put in. GRRR!!

[GPFred]

Had the sensor replaced and its like a totally different car. A dream to drive and power as needed on demand.