Check Engine Light and Fault Codes

Asilver

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I was driving through the city yesterday and the dreaded check engine light popped on. It's actually the first time during my ownership that it's come on and my stomach sank when I saw that amber glow. It still drove fine and wasn't blinking which tends to mean it's safe to continue driving with, so I dropped off my wife then continued home and pulled the codes with my GAP Tool.

After letting the car sit, the check engine light was gone, but there was still a list of faults that showed up. The only ones related to the engine and which most likely caused the light to come on are P0172 - System too rich (bank 1) and P0175 - System too rich (bank 2).

I really have two overarching questions now:

1. Has anybody run into a situation where both banks are running rich? What would be the first thing to look at when diagnosing? My hope is that it's a sensor or something simple that's triggering both sides of the engine to dump excess fuel, rather then stuck injectors or something like that.

2. After viewing faults, do people typically clear them or keep them logged for future reference?



Below is a list of the other codes which showed up for reference:

Under ABS-Brake Module:
U3003-62 Battery voltage - Algorithm based failure - Signal Compare Failure

BCM-Body Control:
B1B01-87 Key Transponder - Bus Signal/message failure
B1087-86 LIN bus A - Bus signal/message failure - signal is invalid
B112B-83 Steering wheel module - Bus signal/message failure - value of signal protection calculation is incorrect

HVAC-Ventilation:
B1B7B-00 Air Blender Actuator - Rear Left
B1B7D-00 Air distribution actuator - rear

IPC-Instrument Pack:
U2013-08 (2E) Switchpack - General failure information - bus signal/message failure

KVM-Keyless
U201F-31 (68) External receiver - frequency modulation/ pulse width modulation failure - no signal

PBM-Parking Brake:
U3000-16 (20) Control module- General electrical failure - circuit voltage below threshold

RCM-Airbag:
B1A00-16 (2C) Control Module - General electrical failure - circuit voltage below threshold

SASM - Steering Angle:
U0300-55 (6C) Internal Control Module software incompatibility - System programming failure - is not configured


Thank you in advance for any feedback you guys have!

Adam
 

16FujiDisco

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What's the year and milage? My first thought is a vacuum leak or possibly the PCV diaphragm (I can't remember if that trips lean or rich codes).
 

Asilver

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What's the year and milage? My first thought is a vacuum leak or possibly the PCV diaphragm (I can't remember if that trips lean or rich codes).
It's a 2011 with 105k on the clock.

Vac leak makes sense. Won't be too much fun to try and track down. I'm going to see if I can get a shop to do a smoke test on it to start.
 

jlglr4

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Vac leak and PCV will typically trip lean codes, not rich - unmetered air gives a lean condition.

MAFs can fail in either direction (underreport/overreport, lean/rich) so that’s a possibility. If either MAF fails, it will affect both banks (the two airflows are combined at the throttle body, and the car just uses the combined MAF values to calculate the fuel mixture).

Fuel pressure regulator would be a possibility, but I’m not sure if this car has one. Anybody know? I think it might regulate pressure just through the individual rail sensors and the HP fuel pumps, in which case both sides would need to fail.

I think the EVAP purge valve is another possibility and known failure item. Its only supposed to open when the car is at higher RPMs (low vac) to allow the tank to vent. If stuck open at idle, the high vacuum from the engine can pull in fumes from the tank giving a rich mixture, although it should lean out once you start driving. If you have a GAP tool or the like, you can use live values to watch your fuel trim as you drive. With a rich code, you should see high negative fuel trim (ecm trying to back off on the fuel supply).

If the purge valve is stuck closed all the time, pressure builds in the tank - not sure what effect that would have on the fuel pump/pressure (if any), but you should hear a hissing when opening the gas cap if its stuck closed.

Coolant temp sensor malfunction can also create havoc with the fuel mixture. There are two that work together - one just below the T-stat in the front, and one on the rear crossover pipe. I believe failure of either one can cause problems.

Nothing else really comes to mind that would likely affect both banks. Obviously, two components could fail (one on each bank), but doesn’t seem likely.

As for the codes, I typically clear then and see if they return, especially if its been a long time since you ran the codes. You can take a screen shot or list them out for your records (as you did here). I don’t see anything in that list that would affect your engine or fuel system.
 

greiswig

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As usual, I think @jlglr4 's logic is really sound, and he's making good recommendations. The only thing I might add to what he said is to check the condition of the battery and alternator in case there is a problem with voltage leading to some of the seemingly strange mix of codes.
 

jlach993

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I've had those two exact codes in the past. Clean your MAF sensors with maf cleaner. That's probably it. If it comes back then your sensor/sensors are failing. I think it trips for both banks, even if its just one thats dirty/defective.
 

LR4 2011

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I currently have P0172 Bank 1 rich. I cleaned the sensors and it returned within 1 mile of driving.

I have ordered 2 PCV valves because a stuck open valve will allow more unburnt gases than normal and richen the right side.

If that does not fix then I will move the sensor to the other side and see if the error swithces to Bank 2.

Next would be to see if a particular plug is fouled which may indicate a fouled/leaking injector.

Next would be for me to investigate the Up stream O2 sensor to see if it is functioning, possible swap sides to see if code follows.

2011 LR4 110,000 miles
 

jlglr4

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By cleaning/switching the “sensor,” I assume you mean the MAF sensors on the air intakes? The two air boxes combine at the throttle body, so a faulty MAF should affect both banks equally. Likewise, PCV dumps into the throttle body, so a faulty PCV should affect both banks, and generally gives a lean code rather than a rich code (failure is usually a tear in the diaphragm that allows unmetered air). Seems like an o2 sensor is more likely.

Do you have a GAP tool or other scanner that can read fuel trims, o2 sensor readings, and/or maf readings?
 

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