🔧 Technical Looking for some technical help!

[Outlaw]

Looking for some technical help.

2008 Sierra 1500 with a 4.3. 323,000 miles.

Truck was experiencing poor fuel economy and had a CEL. Codes:

-PO050- Ho2S heater control circuit B2 S1
-PO059- Ho2S heater resistance B2 S1
-PO154- o2 circuit no activity detected B2 S1
-PO155- o2 sensor heater circuit B2 S1

Looking at live data bank 2 upstream was hovering right around .450 for the most part, no LTFT corrections, etc. Sweet, easy peasy throw a new pair of upstreams at it.

Just replaces both using Denso sensors (part # 234-4337) and cleared the codes, light came back on immediately. Truck still has the PO050 and 155 code. Checked fuse 8 and 18 for o2 sensors, both are fine. Now, after about a minute after startup the truck misfires and throws a flashing CEL. No misfire codes, but misfire history on cyl 2,4 and 6 and I can watch the misfire count on live data. After 3-4 min of misfiring at idle it clears up and runs great. Zero misfire count to speak of. To the best of my knowledge from messing with this for the past hour or so once it stops it will not start again until you shut the truck off and restart.

Any ideas? As far as the o2 heater goes, I’m going to assume it’s a bad ground or messed up wire going to the sensor, but the newly found misfire issue has me confused.

Thanks in advance!

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[Yaj Yak]

Vac leak?

 

[Outlaw]

I’m leaning towards something with the o2’s considering the misfire is directly linked to replacing the sensors

 

[Rdrnnr]

I’m leaning towards something with the o2’s considering the misfire is directly linked to replacing the sensors

The o2s working right could be pissin off the pcm cuz it can't keep it in spec? I know I've had vacuum leaks do just this on my 3800 and give me nightmares

 

[zenriddles]

Go over you fuses with a fine tooth comb.

 

[Outlaw]

The o2s working right could be pissin off the pcm cuz it can't keep it in spec? I know I've had vacuum leaks do just this on my 3800 and give me nightmares

I’m going to drive it a bit more before I start doing anything drastic. The misfire goes away in about 2 minutes of idle and way faster if you drive it. I don’t want to be chasing a problem that doesn’t exist.

I still think something is definitely wrong with the o2 heater wiring.

I did confirm this evening the sensor is working, was watching it go between .800’s and .050’s.

 

[Outlaw]

Go over you fuses with a fine tooth comb.

Will do.

 

[Rdrnnr]

I’m going to drive it a bit more before I start doing anything drastic. The misfire goes away in about 2 minutes of idle and way faster if you drive it. I don’t want to be chasing a problem that doesn’t exist.

I still think something is definitely wrong with the o2 heater wiring.

I did confirm this evening the sensor is working, was watching it go between .800’s and .050’s.

Could be an intake gasket leak that seals up as it warms up

 

[Rdrnnr]

Thatd usually throw a lean code tho

 

[SaturdaysGS]

Bad new sensor (heater)? Or wiring I’d think, any crusties in the connector?

 

[Turbocharged400sbc]

There's a good possibility it's had one transmission at least and they may have pinched the sensor wires in between the engine and trans it sounds like whatever they did pinched 2 of the 4 wires which is why I'm throwing this out there.

Also once you clear the codes you reset all the adaptive's and so now it is trying to go back to base fueling which might explain the misfire suddenly appearing. Fix the 02 circuits and you'll probably get rid of that misfire issue

 

[Turbocharged400sbc]

Thatd usually throw a lean code tho

Dont count on it.

 

[Rdrnnr]

Dont count on it.

Well, sometimes. I know every ls I've owned has needed em at one point or another. And if you don't change at least the back knock sensor while your down there itll piss you off with a light a week later every time [emoji23]

 

[CMNTMXR57]

Sounds to me like a bad ground somewhere in the circuit.

Conditions for setting the DTC;
P0050 or P0056
• The ECM detects that the affected HO2S heater low control circuit is not within a specified range at engine start-up.

• DTCs P0050, and P0056 set within 1 second when the above condition is met.

P0155
• The ECM detects that the HO2S 1 heater current parameter is more than 3.125 amps or less than 0.25 amp.

• DTC P0155 sets within 120 seconds during the heater current test when the above condition is met.


Circuit system/verification
1) Allow the engine to reach operating temperature. With the engine running, observe the HO2S Heater parameter with a scan tool. The value should vary from below 2A to above 1A.
2) With the engine running at operating temperature, observe the HO2S Heater parameter with a scan tool and manipulate the related wiring and connectors.
⇒ If manipulation does affect the parameter then repair the harness or connector.

3) Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/Ststem 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 control circuit terminal D and the appropriate HO2S heater low control circuit terminal listed below:
• B1S1 terminal C

• B1S2 terminal C

• B2S1 terminal C

• 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.

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 C

• B1S2 terminal C

• B2S1 terminal C

• 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.

 

[Turbocharged400sbc]

Remember he's a diesel guy....ya may need to dumb that down some

 

[Outlaw]

There's a good possibility it's had one transmission at least and they may have pinched the sensor wires in between the engine and trans it sounds like whatever they did pinched 2 of the 4 wires which is why I'm throwing this out there.

Also once you clear the codes you reset all the adaptive's and so now it is trying to go back to base fueling which might explain the misfire suddenly appearing. Fix the 02 circuits and you'll probably get rid of that misfire issue

I ended up doing a global relearn on it yesterday afternoon since I never did after replacing the sensors. It didn’t misfire once the rest of the day, light is now back on obviously for the heater still

Remember he's a diesel guy....ya may need to dumb that down some

I get the jist of it lol, I’m going to continue to mess with it today, just happy that for now there’s no more misfire for now.

I did check all the fuses individually, none were visually bad.

 

[Turbocharged400sbc]

Did you get a chance to look behind the engine with a mirror?

I figure you should be able to at least figure out how a mirror works

 

[Turbocharged400sbc]

And don't forget whoever was the knucklehead that might have replaced that sensor before you did may have yanked one of the terminals out of the back of the connector housing take a close look at the way the wires kind of make a hard Bend out of the grommets and make sure you can't see any fresh clean insulation

 

[Turbocharged400sbc]

Remember it's the side without the release tab that usually gets the wires yanked out of it since most people just grab onto the loom and grab onto the release tab with one finger and then yank

 

[Turbocharged400sbc]

I'll help you out here just drop it off at my house and put the title in the glove box.

I sort of have a thing for Junk V6s

 

[Ron Vogel]

If you’re chasing vac leaks, check the injector seats. You can hear leaks easy with a hose up to your ear. IIRC, 3800’s have a shared circuit for the O2’s, MAF, and something else. Might be ignition? I do know for certain that power for ignition spark goes through the key tumbler. I took mine apart and cleaned all the carbon off the contacts and it helped with misfires. If you do this, it’s not fun. Lots of little springs can shoot out of it. Pain to assemble.

 

[Outlaw]

Sorry to leave y’all hanging. I’ve spent the past three days getting a new plow truck setup that was an utter disaster.

Only update on this truck I have is the misfire came back, but not nearly as often or predictable since the global reset.

Depending on how much snow we get tomorrow/Tuesday I’m going to be pretty much stuck doing that. Hoping to have some time to mess with it later in the week.

 

[Rdrnnr]

Outlaw you Got any live data on this thing per chance? Especially when its acting up?

 

[Outlaw]

I don’t have any stored but I can record some next time.

 

[bikrboy128]

Isn't .450v the default the ecm will readout if the o2 is unplugged? I'd be checking wiring like Turbo400 suggested, sounds like you have a break somewhere