Thread: P0172 [Bank 1 Rich] on a 2001 GTP

Alright, so I've got this car: [ http://www.grandprixforums.net/threa...h-P0172!/page6 ] that I'm trying to figure out.

A brief history: Did a trans swap, rad replacement, valve cover replacement, and some other minor maintenance things. Shortly thereafter it presented with a P0121 (Throttle position sensor fault) and very little boost. Also, it would hold gear way too long while accelerating. I attributed that to the TPS issue. I replaced the TPS with no change. (I can't believe I though it would be so simple as, read code, replace part. When does that ever happen?) Further investigation showed a broken/cracked vacuum boot at the MAP sensor. I replaced EVERY vacuum line on the engine and got my boost back. This also resolved the P0121 (TPS) code.

HOWEVER, after fixing the MAP vacuum line issue, it started having a pending P0172 (bank 1 rich) code. Trims have slowly been creeping down to the point where a pending P0172 became an active P0127 (between -15% and -20%). Here's what I've done so far with no resolution;

1.) Verified O2 sensor activity between 0.2v and 0.8v while oscillating the throttle watching the graph on VCM Scanner. Seems to react as quickly as it should.
2.) Cleaned the MAF, throttle body, and IAC. For grins, I also swapped the MAF with a known good unit.
3.) Briefly checked all wiring and extensively for the O2 sensor. -All good
4.) Checked fuel pressure during operation, and after key off for bleed down. -Within range (43psi)
5.) Disconnected the purge solenoid from the throttle body, and capped both sides.

Things I haven't done or plan to do in this order;

A.) Put fresh fuel in it. Unlikely that it's contaminated, but I have to rule it out. (Doesn't this typically cause a lean condition?)
B.) Swap the MAP with a known good unit. Sure it would be nice to test the "proper" way, but I don't have a hand vacuum pump. Best I can do is swap it.
C.) Swap the purge solenoid with a known good unit.
D.) Swap the front O2 with a known good unit.
E.) Say Eff it, burn 2 HPT credits and scale the cylinder gain to about 1.3125.

Anyone have any other ideas for a P0172 on one of these?

Reset fuel trims and then let it relearn over the course of a few days varied driving. See if the issue exists, you did stuff and instead of letting it creep down.. reset it. See what is real.

If it still exists see what makes sense from this.
http://www.gearchatter.com/viewtopic8736.php

A leaking injector etc could do it.

Thanks Bill. I've been using the trouble tree on that gearchatter website. Pretty helpful.

I'll dump some new fuel in it, and reset the trims.

I half wonder if this has been a reoccurring issue. Shortly before we bought the car, PO replaced the EGR, injectors, and the MAF is newer... Correct me if I'm wrong, but if everything checks out, the only solution is to flash the PCM, correct?

Not at all..

Something is off, something that shouldn't be. Code shouldn't toss unless something is up.

Okay. I'll keep digging.

Originally Posted by BillBoost37

A leaking injector etc could do it.

Just sitting here thinking about this thing (probably too much). Do you think a leaking injector leave any evidence on the corresponding spark plug?

-Reset trims via battery disconnect,
Got fresh gas,
All plugs look good,
Swapped good stock injectors,
Swapped good MAF sensor,
Swapped good MAP sensor,
Swapped good purge solenoid,
Swapped good EGR,

Problem persists.

O2 sensor checks out. Bounces between 0.2v and 0.8v pretty consistently.
Fuel pressure sits at 45psi at idle.
No exhaust leaks.
PCV valve rattles.
Every vacuum line is new.

I half wonder if this hasn't been a problem for a long time and just recency presented itself. When we bought it, the trans was out, so we couldn't test drive. I did scan for codes, and nothing showed, but it could have been sitting with the battery disconnected before we saw it. Anyhow, the reason I suspect this is because PO told me he replaced the injectors, and EGR. Plus, I see the MAF, MAP and purge solenoid valve look new. All these things are possible rich condition causes.

Think I'll drive it for a little while with all the swapped good parts. If the P0172 comes back, I'm burning a tune. Other than a PCM or wiring issue, there is literally nothing else it could be. Unless someone knows something I don't.

I'm having the same problem now. Did you ever resolve the issue?

I threw in the towel. Burned a tune... Adjusted the cylinder gain to 80%. Still running like a champ 3 months later.

Thanks guys! Now I know what direction to head.