Confused Equinox Lean and Rich

Ric Owner/Technician New Hampshire Posted   Latest  
Delayed
Driveability
2013 Chevrolet Equinox LT 2.4L (K LEA Gas) 6-spd (6T45) — 2GNFLEEK2D6386028
P0131 — O2 Sensor Circuit Low Voltage Bank 1 Sensor 1
P015B — O2 Sensor Delayed Response - Lean to Rich Bank 1 Sensor 1
P0171 — System Too Lean Bank 1
P0172 — System Too Rich Bank 1
P2096 — Post Catalyst Fuel Trim System Too Lean Bank 1
Check Engine Light On
Sometimes Runs Poorly
Engine Runs On After Shutdown

Hello Diagnostic Folk.

I have the Equinox with some strange symptoms. This vehicle is a regular with us. Recently went to the dealer for oil consumption fix as it was using a lot of oil. I monitored the O2 and jumped the gun on replacement as I figured it was contaminated. Lots of buildup on the sensor but it made no difference. When first started, the O2 will be zero long enough to set the P0131 pending. Fuel feedback is then shut down. If I clear the codes after a brief warmup and restart, all returns to normal. Trims good and sensor switching. Then as you drive it the following occurs: at a steady cruise the trims start adding for lean until it maxes out. At idle the trims slowly decrease for rich until it maxes out.

I found that our 20 mile old oil was fuel contaminated, very badly. I found a TSB for HP pump failing and putting fuel in the crankcase. This would explain the rich at idle and the contamination. But I am at a loss on how this may affect the trims first off. Fuel pressure is steady and HP numbers are good between desired and actual. Tested fuel for alcohol and its about 12% . I scoped the sensor and bias. They look good.

This is my first drivability with a DI engine. I don't want to replace this pump only to find I missed something else. Guess I'm a little gun shy after the O2. Any advice?

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Sherman Owner
Texas
Sherman
 

So….. how many miles on it?

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Ric Owner/Technician
New Hampshire
Ric
 

100k

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Jamie Mobile Technician
British Columbia
Jamie
 

Good morning. I would focus on your Oxygen sensor/circuit issue. I wouldn't trust any fuel trims knowing that the O2 circuit does not work correctly. I'm not certain if this vehicle should have a bias voltage on the O2 sensor circuit when inactive. Can you unplug both the front and rear O2 sensors and see what they read on the scantool? Also, have you verified O2 sensor heater operation with a…

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Ric Owner/Technician
New Hampshire
Ric
 

Here is a file of startup.

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Thomas Technician
Virginia
Thomas
 

I would for sure look into that o2 sensor. what does the downstream read? the Cat does not change the ration coming out of the engine. what I mean is ( using john thortons thought) if a lamda of 1 enters the engine then a lamda of 1 should exit the engine, stay the same as it passes the upstream and downstream sensor, it shouldn't change ( with in reason). Is there software update for ECM?

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Spiro Service Manager
New York
Spiro
 

youtube​.​com/watch?v=R9bzIq… Ric, Bernie talks about the bias voltages in the O2 circuit (this video). I hope it will help… Spiro

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Ric Owner/Technician
New Hampshire
Ric
 

Thanks! I have seen this video. Bias voltage was good. No intrusion at the PCM.

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Bentley Manager
California
Bentley
 

I would fix what you have proved is a problem, fuel in oil, first. After that test for other issues.

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Glenn Owner/Technician
Texas
Glenn
 

The plungers fail and leak fuel on the HPFP and this allows excess fuel in the crankcase. The HPFP is run by a lobe on the camshaft. Try blocking off the PCV and the tank vapor line while watching the fuel trims. The PCV is sucking in excess fuel vapor from the crankcase and this will mess with the trims at different RPM ranges. Change the oil again, or run the engine for a while for trims to…

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Darren Technician
Wisconsin
Darren
 

Warm idle , no more than 600 ppm HC in crankcase via dipstick. if so I strongly suspect high pressure pump.

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Caleb Diagnostician
Indiana
Caleb
   

Ric yes the HPFP is the reason for the runon/dieseling. As Glenn said it sucks the fumes back thru the CCV and into the intake richening the mixture. We used to do hundreds of these at the dealer literally. Maybe you have a second problem, however you have to start with the obvious. Be sure to change the oil again after replacing it. Reset fuel trims and see were you are. Did the dealer put new…

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Cameron Owner/Technician
Virginia
Cameron
 

`There is a bulletin for P015B, Update PCM software, did one yesterday. High pressure fuel pumps die all the time also

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Ric Owner/Technician
New Hampshire
Ric Delay
 

Thanks to all who replied so far. I replaced the HP pump. That took care of the fuel in the oil and the rich codes. Lean codes remain but the customer needed the car back. Due to return in a few weeks for more scrutinizing.

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