intermittent CEL and a host of codes

[0RESET0]

I got a CEL out of the blue the other day. I gave it a day to see if it would come out of it. When I pulled the codes the next day I got some doozies. U1064, U1041, P0106, P0135. On the drive homme after pulling the codes the CEL turned itself off. Then this afternoon after work it came back on. Common thread between them seems to be a possible bad connection at the battery. Since I will be swapping out the front Axel disconnect tomorrow, I think I will check and clean the battery connections.

Can any of you think of anything else to try other than replacing a bunch of parts?

[v7guy]

Check that battery connection, make sure it's clean and hooked up correctly then clear the codes and get back to us. No sense chasing problems that may or may not really be problems.

Do you think it's likely the battery is connected poorly?

[0RESET0]

I checked the battery connections today. They seemed to be fine. I had the codes cleared and will wait to see if the CEL comes back. By the way, swapping out the disconnect went really well. 1.5 hours and no issues.

[0RESET0]

OK. CEL came back on today on the way home from work. Stopped and had the codes pulled again. U1064, U1041 and P0135 twice. Do you guys think replacing the O2 sensor would fix the two U codes too? Those two are throwing me for a loop. I did a search of the forum for the codes and turned up nothing. I will see what Google has to say.

[djthumper]

I highly doubt it. Loss of communications and an ABS code.

[Trail X]

I didn't look up the codes themselves, but from what Larry said, I'm assuming something is taking down your can bus. Could be a bad connection or a module that has gone bad. I'd be sure to check gmtn for more info.

[djthumper]

It could be an ABS sensor that is causing a bit of havoc on your data bus and causing it to drop. A quick google search pointed me in the direction, I don't recall any of this popping up on GMTN. I would definitely post it up there, you never know what someone will post up.

[0RESET0]

Thanks guys. My Google-foo must be lacking, I didn't turn up the same results. One was for communication lost to BCM and the other was communication lost to EBTCM, this one could be the ABS that you guys found. My ABS and TC lights have come on in the past but never triggered a CEL. They also usually went away on their own pretty quickly, I attributed them to a dirty sensor. I know it is a long shot but you don't think the larger tires could be doing anything to the signals going to the EBTCM do you? I will get the O2 sensors on their way and do some more research.

P.S. Not a member on GMTN. I will look over there though.

[Trail X]

Larger tires shouldn't affect the EBTCM (ABS module). I believe the EBTCM is simply the valve block that controls the ABS response. I believe that the ABS brains are in the PCM. My truck isn't CAN though, so my FSM doesn't cover the communications bus on the 2006+ trucks.

If you're losing a can bus intermittently, I'd really suspect a bad connection. If its constant, then its likely a bad module.

See if your ABS works first by testing it on a gravel lot or wet pavement. That should tell us if the module has any communication over the bus. If its not working all the time, then you have a bad connection or a bad module that's talking too much and taking down the bus. If the ABS works, but you still get intermittent CELs for a dropping bus, then it may be a bad connection and you'll need to try to identify where the spotty connection is occuring. Could be a lose plug or pin, or a wire that has been compromised. If you get into trying to troubleshoot a bad connection, you'll need schematics and a lot of knowledge of a multimeter.

If a module is taking the bus down, finding said module will probably require a CAN sniffer of some sort - I hate to say it, but it might be a dealer only repair.

[0RESET0]

Thanks Trail X. Can anyone tell me where the EBTCM is? I have seen recommendations for checking the connection on other vehicles so I would like to try that on mine. The CEL light turned itself off again today on the way home from work. Something is definitely intermittent. I replaced the ignition switch when I first got the truck back in 2011. Any chance it could have gone bad again? Some of the stuff I found for other vehicles with CAN BUS codes said that it could be a bad ignition switch.

[Trail X]

I found this image for a reference. Should be right behind the secondary air injection pump, in front of the fuel tank.

[0RESET0]

That picture is worth a thousand words, and a Beer if I ever meet you. Thank you very much. My searching was not turning up anything like that. I did fine several mentions of cleaning up the ground connection. I will do that while I am under there looking at the connectors.

Truck acted really weird this morning. Shortly after leaving my driveway the engine seemed to lose power big time, almost like the traction control was kicking in but with out the light coming on. As of parking it this morning at work, the CEL was not on. I have had little blips of the "no power" thing before but nothing like this. I had to modulate the gas pedal several times to get it to come out of it.

[rScherzer]

Though I would share some info here for you. The P0106 is for the MAP sensor performance. "This doesn't mean the MAP sensor is bad, its more like the sensor is reporting a signal that the computer didn't like. There is a PIP from GM PIP4015A. Basically look at the throttle blade and if its got a bunch of carbon build up on it, then that could possibly set this particular code. I have also seen the intake manifolds loosen up near the rear and set this code, but most of the time they are accompanied with a lean code.

The p0135 , is for the heated o2 sensor. Most cases if the fuse is good, its a O2 sensor on the way out the door. I believe the fuse is #29 in the under hood fuse block.

The U Codes are a bit more tricky. This is a possible fix for the EBCM / ABS module. I personally have tried it and did not fix any thing but for the cost it was worth a go. On the left frame to body mount under the drivers door towards the front there are a few black wires with small bolts threw them. If the grounds get dirty / high resistance , the module on that ground will not power up correctly. If you take loose the bolt and clean the mounting surface and the connecting side, this might fix your U1041. The other one is for the BCM I think. Would really need to know it the U codes were currant or history.

[0RESET0]

OK. O2 sensors are on order from rockauto. I checked the connections James mentioned, my ebcm only has one big connector instead of the two shown in the picture. While I was down there I checked the 12 gauge ground wire. The bolt was rusty. Since the factory does not remove paint when they install these, the threads of the bolt and nut are the only connection. I ground the paint off, cleaned up the back of the wire tab and used a glob of dielectric grease before reinstalling the bolt. Before I started the whole thing, the CEL was on. When I finished and started the truck, the light was off. I will let you know if it comes back.

Anyone have any tricks for reaching the connector for the rear O2 sensor? I can shove my arm in there but it is tight.

[0RESET0]

Though I would share some info here for you. The P0106 is for the MAP sensor performance. "This doesn't mean the MAP sensor is bad, its more like the sensor is reporting a signal that the computer didn't like. There is a PIP from GM PIP4015A. Basically look at the throttle blade and if its got a bunch of carbon build up on it, then that could possibly set this particular code. I have also seen the intake manifolds loosen up near the rear and set this code, but most of the time they are accompanied with a lean code.

The p0135 , is for the heated o2 sensor. Most cases if the fuse is good, its a O2 sensor on the way out the door. I believe the fuse is #29 in the under hood fuse block.

The U Codes are a bit more tricky. This is a possible fix for the EBCM / ABS module. I personally have tried it and did not fix any thing but for the cost it was worth a go. On the left frame to body mount under the drivers door towards the front there are a few black wires with small bolts threw them. If the grounds get dirty / high resistance , the module on that ground will not power up correctly. If you take loose the bolt and clean the mounting surface and the connecting side, this might fix your U1041. The other one is for the BCM I think. Would really need to know it the U codes were currant or history.

Thanks. P0106 has not come back after being cleared once. I doubt the sensor or tb has ever been touched in the 100k plus mile life of the truck. The sensor is cheap so replacement is on the list. I have had the codes cleared and checked again after the CEL came back. Current codes were U1064, U1041 and P0135.

[0RESET0]

OK today I try to install the new sensors. Wish me luck. Still not sure how i am going to get the rear one disconnected but I will see what I can do.

[0RESET0]

Sensors are installed. Took me about an hour. That rear one was a real PITA! I had the codes cleared when I was done. I will let you know if anything comes back.