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Pete
Pete, Auto Service Technician
Category: Chevy
Satisfied Customers: 24725
Experience:  14 years GM dealer Technician.
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Gets very weak when it heats up but not to strong at first

Customer Question

Gets very weak when it heats up but not to strong at first either, lugs at low throttle exceleration. Dealer changed cats because of bank 1 efficency code. Didn't help. I changed o2 sensors then both bank sensor 2 heater circuit codes. Changed again with ac Delco same code. Checked fuel pressure 55 psi at idle drops to 50 psi when accelerate. Bank 1 sensor 2 has soot on it after 1000 miles. Feels like it could be missing but no other codes
JA: Have you located all of the vehicle's oxygen sensors? Are the wires leading to and from each intact and in good shape?
Customer: All 4 sensors have been changed, wires seem to be ok
JA: What is the model/year of your Chevy?
Customer: 2008 2500hd 6.0
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: Seems the dealer can't so I'm trying. Besides the o2 sensors , I cleaned maf and throttle body, changed foot pedal and crank sensor
JA: Anything else you think the mechanic should know?
Customer: Bought fuel pump but haven't installed
Submitted: 3 months ago.
Category: Chevy
Customer: replied 3 months ago.
Installed high flow muffler after cat change, checked both fuses labeled o2
Customer: replied 3 months ago.
200rpm surges
Customer: replied 3 months ago.
Runs better for almost a day if you disconnect the battery but still not right
Expert:  Pete replied 3 months ago.

Hi my name is ***** ***** I will be happy to assist with this today.In some cases I may need more info to assist better.I apologize for any delay.

Did the dealer ever check for a vacuum leak at all?

Let me know so we can continue,thanks Pete

Customer: replied 3 months ago.
I don't know what they checked for. I sprayed around the intake and didn't notice any change in how it runs
Expert:  Pete replied 3 months ago.

Are any fault codes setting with this issue now?

Customer: replied 3 months ago.
Like in the description o2 heater circuit codes p0054 and p0060. These codes set when the o2 sensors were changed because I thought the mapping was off. Idle improved dramatically after they were changed. I replaced them again with ac delco
Expert:  Pete replied 3 months ago.

Did you check for any corrosion or damage to the connectors at the oxygen sensors at all?

Customer: replied 3 months ago.
The connectors look new
Expert:  Pete replied 3 months ago.

Do you have a scan tool to check engine data signals (specifically the heater signals at the oxygen sensors) as well as a multi meter to test electrical at all?

Customer: replied 3 months ago.
Actron cp9670. Graphs individual reading not much more to it. Yes I have a multimeter
Expert:  Pete replied 3 months ago.

O.k.,at the pink wire or pink wire with black stripe at each oxygen sensor are you getting at or near 12 volts dc with the key on?

Customer: replied 3 months ago.
Expert:  Pete replied 3 months ago.

O.k.,with the connector unplugged at oxygen sensor bank 1 sensor 2 test for voltage at the pink wire while using the gray wire with white stripe in terminal C for ground and see if you have a ground on C at all with the key on and let me know.

Customer: replied 3 months ago.
10,72 . 12.56 to frame
Customer: replied 3 months ago.
Any idea where the ground terminates I don't have a schematic
Expert:  Pete replied 3 months ago.

I apologize for the delay.There should not have been a ground signal at all on this wire here at the sensor connector.This indicates that either the wiring is shorted leading to the ecm causing all of these issues here or the ecm itself is faulty needing replaced.I would trace and inspect the wiring leading to the ecm to see if any issues are found.If all wiring is found to be o.k. then the ecm needs replaced to correct this fault here.

Let me know if you need anything else.Feel free to rate my help here,a 5 star rating is appreciated.

Thanks Pete

Customer: replied 3 months ago.
What pin does it go to on the ecm
Customer: replied 3 months ago.
How does a heater work without a ground
Expert:  Pete replied 3 months ago.

The ground control comes from the ecm but only when needed.This wire should not have a ground,here is what the diagnosis says for this testing:

1. Ignition OFF, disconnect the harness connector at the appropriate HO2S.
2. Ignition ON, verify that a test lamp illuminates between the appropriate HO2S heater voltage supply circuit terminal D and ground.

^ If the test lamp does not illuminate, test the HO2S heater voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal and the HO2S heater voltage supply circuit fuse is open, test all components connected to the fuse and replace as necessary.

3. Ignition ON, verify that a test lamp does not illuminate between the appropriate HO2S heater voltage supply circuit terminal D and the appropriate HO2S heater low control circuit terminal listed below:

* B1S1 terminal E
* B1S2 terminal C
* B2S1 terminal E
* B2S2 terminal C

^ If the lamp illuminates, test the HO2S heater low control circuit for a short to ground. If the circuit tests normal, replace the ECM.

Customer: replied 3 months ago.
Test light does not illuminate
Expert:  Pete replied 3 months ago.

Here is the rest of the procedure for code P0054.See if you can follow it.I suspect this is still a wiring issue or internal ecm fault needing repaired or replaced with the issues described here.

4. Engine running, leave the test lamp connected from the previous step. The lamp should flash or be ON steady.

^ If the test lamp is not ON steady or flashing, test the HO2S heater low control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.

Important:
* The output driver should detect a short to voltage and turn OFF. If a resistance fault is present the driver will remain ON and the scan tool will display more than 0.0 amp. Less than 10 ohms may set a DTC.

* Performing this test may set additional DTCs.

5. Ignition OFF, install a 30A fused jumper wire between the appropriate HO2S heater voltage supply circuit terminal D and the appropriate HO2S heater low control circuit terminal listed below:

* B1S1 terminal E
* B1S2 terminal C
* B2S1 terminal E
* B2S2 terminal C

6. Engine running, verify the appropriate scan tool HO2S Heater parameter is less than 0.1 amp.

^ If more than the specified range, test the HO2S heater voltage supply and HO2S heater low control circuits for more than 1 ohm. If the circuits test normal, replace the ECM.

7. If the ECM and all circuits test normal, replace the appropriate HO2S.

Thanks Pete

Customer: replied 3 months ago.
It flashed, 7 ohms and no shortage to ground. Can the ecm cause the fuel pressure drop as well
Expert:  Pete replied 3 months ago.

If the ecm is not supplying the correct signals to the fuel pump relay intermittently like a poor ground feed turn on signal it can cause fuel pressure issues here.You would need to test the fuel pump relay circuits to see if the ground signal from the ecm is a poor signal or no signal at all when the fault occurs with fuel pressure drop or loss.

Thanks Pete