What could cause all four 02 sensors codes to continue to show

Tiny
BOHAIR
  • MEMBER
  • 2007 CHEVROLET EXPRESS
  • 96,500 MILES
On computer even after all sensors were replaced? I have a check engine light that has been on before I bought vehicle. I had the codes checked and all four o2 sensors are displayed on computer. I replaced all four o2 sensors and check engine light remained. I took it to the local auto parts store to have them check codes and they retrieved the same codes as I had before replacing all sensors.

The salesman said he could reset the codes so he did. I still had the check engine light on so same day I went to another auto parts store and asked to have codes checks to confirm issue. They came up with the same codes and the salesman let me use the hand-held computer to reset the codes myself. Check engine light remains on. The vehicle runs great about 9 out of 10 times.

Occasionally, the vehicle will do something weird. About 1 out of 10 times driving the vehicle, I notice that the vehicle will not allow me to drive faster than 30 mph. Sometimes when this happens, I would be going over 30 mph (and the engine will not response to depressing accelerator and the speedometer will descend. If it drops under 30 mph, then I can accelerate upto 30mph but no greater.

When the vehicle speeds over 30 mph, the engine doesn't respond (still running though). The motor does not run eratic and it seems like the engine has a perfect governor at 30 mph. I will try several times to go over 30 and it will not let me. However, when I pull over and turn engine off and restart the vehicle, there is no longer an issue until about 10 engine starts later.

A friend looked at it and seen the same codes and said he seen an evap leak code (low or High?). I replaced the gas cap and never seen the code when I went to the autoparts store. I don't know if that might be the issue for 30mph problem. However, the check engine light remains on with all 4 o2 sensors.
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Monday, April 2nd, 2012 AT 2:25 PM

14 Replies

Tiny
HMAC300
  • EXPERT
You might have a pluggegd converteror converters. Put a vacuum gauge on the intake and if it reads 15" or below at idle suspect that. That could be your 30mph reason as well. But before you do that take it to a pro to see if the O2's are reading lean or rich as that could be another problem causing this. The hand held ones won't tell you if it's lean or rich just that it's a O2 sensor problem.
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Monday, April 2nd, 2012 AT 4:27 PM
Tiny
WRENCHTECH
  • EXPERT
What are the code numbers that you are receiving?
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Monday, April 2nd, 2012 AT 4:46 PM
Tiny
BOHAIR
  • MEMBER
Thank you both for quick reply. The specific troubleshooting codes are: P0036, P0054, P0056, and P0060. Some were showing to be repeated. Thanks
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Monday, April 2nd, 2012 AT 9:48 PM
Tiny
WRENCHTECH
  • EXPERT
Those are all heater codes. You can't have 4 sensors with burnt out heaters so you have either a power interruption or a ground interruption.

They are powered in pairs so that is highly unlikely also. The only thing all 4 share is a common ground. That ground is #G103 on one of the bell housing bolts so check that first.

You can unplug one of the sensor and test for power and ground. All the power supply wires are pink and get power in run/start. The ground goes through the PCM and they are different colors for each sensor.
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Monday, April 2nd, 2012 AT 10:12 PM
Tiny
BOHAIR
  • MEMBER
Solution found! Thanks for the diagram. Power interrupt was the problem as you suggested. I had no idea that there was a fuse box under the hood also. Anyways, I located the two fuses as listed per diagram and one of the two fuses was burned. I replaced the one fuse. Check engine light does not come on anymore. Thanks!
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Sunday, April 15th, 2012 AT 4:49 AM
Tiny
WRENCHTECH
  • EXPERT
You're welcome. Be advised that something caused that fuse to burn so there may be an underlying circuit overload/short circuit that you haven't found yet so it could happen again.
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Sunday, April 15th, 2012 AT 11:55 AM
Tiny
BOHAIR
  • MEMBER
Good call! I have looked at the old sensors that I had replaced and one of the wires had frayed where it looks like it rubbed against the chasis. There is no engine light on but there is a pending diagnostic code that I have now that is P0060. I'll drive the truck around and see if the other previous codes appear again and check to see if the fuse is remaining intact and give an update. Thanks
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Monday, April 16th, 2012 AT 2:51 PM
Tiny
BOHAIR
  • MEMBER
I have tested all wires for all 02 sensors. I tested pink wires for 12V with ignition turned on. I also tested the other three wires for each sensor for continuity from each o2 sensor connector and corresponding PCM connector pin and for short by connecting multimeter lead to each non-pink wire and other lead to chasis. All wiring passed. I also tested four ground pins from PCM connector and all checked good. P0060 still comes back after clearing code so I decided to remove the o2 sensor (Bank 2, sens 2). The sensor was replaced not to long ago (couple of months) and the end has black residue all around it. Would that suggest that the converter is clogged? It is hard to see the black residue in picture because I wiped some of it off. If so, I'll go ahead and take it to an exhaust shop as suggested in first reply of this topic. Or whatelse should I test/do before taking it in to a shop. Thanks (sorry for waiting so late to respond-have little time to work on truck)
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Tuesday, May 8th, 2012 AT 12:14 AM
Tiny
WRENCHTECH
  • EXPERT
NEVER wipe an 0/2 sensor. They are in the exhaust pipe, they are supposed to get black.
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Tuesday, May 8th, 2012 AT 12:18 AM
Tiny
BOHAIR
  • MEMBER
I noticed that the bank 1 sensor 2 only had a tiny amount of residue, nothing compared to Bank 2 sensor 2. That is why I was concerned.
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Tuesday, May 8th, 2012 AT 12:42 AM
Tiny
BOHAIR
  • MEMBER
Hi Wrenchtech,
Your help has been tremendous. Would you have any other insight to my last reply. I have donated $50 ($20, $20, $10)so far since I have entered first question. I will continue donate as long as I keep trying to get your knowledge. Is there somethingelse that I can do before taking vehicle to exhaust shop? Should I even take it to the exhaust shop? The only direction that I have is you and you have helped me a lot. I don't have a vacuum gauge or specialized tools for troubleshooting. If there are no more suggestions, I'll just take it into the shop. Thanks
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Tuesday, May 8th, 2012 AT 8:19 PM
Tiny
WRENCHTECH
  • EXPERT
You're down to one sensor and one problem. Bank2 sensor2. You either have a bad heater in the sensor or a problem with the wiring. What I would try is swapping the 2 downstream sensors and clear the computer to see if the same code comes back, eliminating the sensor as the cause. If the code changes to the other position, then you have a bad sensor.
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Tuesday, May 8th, 2012 AT 8:25 PM
Tiny
BOHAIR
  • MEMBER
Wrenchtech,
I switched the bank 2 sensor 2 with Bank 1 Sensor 1 and code changed from downstream to upstream. I replaced sensor and no codes were produced after 100 miles had been added. I am grateful for all your help. It was fun tracing wires on a car for the first time. I hope my vehicles don't break down again, but if they do, I'll definately come back to 2carpros. Com. Thanks.
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+1
Monday, May 14th, 2012 AT 2:29 AM
Tiny
WRENCHTECH
  • EXPERT
Glad to hear it all worked out for you.
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Monday, May 14th, 2012 AT 9:50 AM

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