4wd service codes

[h45wt]

We're traveling and have been having some odd issues with 4wd indicators. Truck is described in the signature line and has the electric transfer case (3 button) panel. I've been seeing intermittent "service 4wd" on the dic now for a few weeks. Later I noticed the 4x4 neutral indicator and service 4wd on. Codes were p1172, p1637 generator-L-terminal circuit, p0266, p0267, p0268, nd099, nd024, cleared codes, next morning 4x4 low indicator on with check engine light, codes p0500 speed sensor malf, p0700 tcm malf, drove 60 mi to yuma, cleared codes and all looked normal. next morning service 4wd indicator came on, no active codes but "not run codes" were p0540 and p0543, p1172, p1637, p0266, p0267, p0268, nd099. I was thinking about pulling the tcm fuse just in case but don't know what it is called in the fuse panel.

Don't want to get stuck on the road home as the are long lonely roads and it will still be really cold through Canada.

Any suggestions as to what part may be failing based on the codes I've listed?

What does the "codes not ran" on the Predator diagnostic screen mean?

Thanks

[More Power]

The most frequent cause of the sort of problems you're seeing is the pushbutton switch panel. I had the same problem, and simply replaced the switch panel with a new one. Solved the problem... and the local dealer parts guys said they replace them quite often. Mine was replaced about 3 years ago, and it's still working fine. It was about $40 if I remember correctly.

On another note, my wife's AWD Chevy Tahoe also had problems with its 4WD indicator system. Again, I simply replaced the switch panel.. Problem solved.

Jim

[h45wt]

The most frequent cause of the sort of problems you're seeing is the pushbutton switch panel. I had the same problem, and simply replaced the switch panel with a new one. Solved the problem... and the local dealer parts guys said they replace them quite often. Mine was replaced about 3 years ago, and it's still working fine. It was about $40 if I remember correctly.

On another note, my wife's AWD Chevy Tahoe also had problems with its 4WD indicator system. Again, I simply replaced the switch panel.. Problem solved.

Jim
Jim,

Thanks for the info.

I pulled the 4wd fuse more than a week and hundreds of miles ago. I've had no more faulty indicators. The service 4wd light comes on every time I start the engine but that is understandable.

Would this argue that the fault is in the encoder or might it still be the switch unit? I would think that no faults while the fuse was out would point more to the encoder.

[DmaxMaverick]

I've seen few of these, as well as mine. The button cluster was the cure, each time. I know of one encoder motor failure, and there was no "Service 4wd" message, and no DTC. I'm not sure why there would be no message with the fuse pulled. Never tried that. I'll pull my fuse to see if the message appears (no 4x4 issues at this time), and get back later.

[h45wt]

I guess I spoke too soon. 4wd fuse still out and today backing out of parking space I felt/heard a thump. No bodies or debris behind or underneath truck. A few miles later saw the 4wd low light flashing. Restart no change. Pressed 2wd button and 4wd low light went on solid, 2wd started blinking. After 2 restarts no chg but ck eng light on. New dtc p0700 tcm malf. tried to reset but would not erase. After a few more restarts I was able to clear the p0700 and the ck end light went out. all looks normal now except for the service 4wd msg at each restart probably due to the fuse being pulled. Don't know what the thump was, perhaps transfer case or drive line. I guess this latest symptom would argue for the switch panel failure. Unless something else pops up I'll get a new one when I get home. Any hints on steps to replace it?

[DmaxMaverick]

Easy to replace....

Tilt wheel all the way down, set the E-brake, and move gear selector to 1 (they get in the way if you don't). Pop off the IP bezel. It's one piece from the far left to the right of the radio/HVAC. Just pull it gently from edges you can get a grip on (with fingertips, starting at the radio corner area), all the way around until it's free (pull only enough to free the clips, not too far). The switch cluster has friction tabs holding it in (and maybe a screw, I don't remember, but it should be obvious), just engage them with a finger or screwdriver and pull the switch out. Unplug. Reverse for install.

Same procedure for all the in-dash switches and accessories (headlamp switch, radio, HVAC head, etc.). Very simple.

If for any reason a bezel clip tab doesn't lock in solid (and creates a rattle/squeak), wrap the tab with one or two layers of scotch tape, depending on how loose (it doesn't take much). It will snug it up just right. If you bend a tab, reinstall it bent, if at all possible. Bending them back usually breaks them off.

[h45wt]

After we returned from our travels I reinstalled the 4wd fuse to see if the problem would return. After a couple of months the indicator lights started giving false indications again. Then in July I started to hear a slight knocking noise in the front half of the drive train. The dealer felt the problem was in the front differential so they ordered all the parts for a rebuild. It took more than 5 weeks to get all the parts here. They found the spring that operates the 4wd shift collar in the front differential was broken. $400 labor to replace a $7 part. The work was finished in late August and I have had no more false indicators in the 4wd panel.

My question now is, could that shift collar problem have been causing the false panel indications? Is there a sensor somewhere that was trying to warn me of the impending failure? None of the codes I saw were specific enough for me to identify the problem even when it failed completely. Could the dealer have figured this out before it failed completely?

[h45wt]

I am updating this thread as my code and light issues continue. Since the original problems in Feb/Mar of 2009 we haven't been on the road. Use around our small town has not given me many codes. In a previous post in this thread I did have the front differential repaired last July when the spring that holds the axle engagement collar broke. $400 to replace a $7 spring.

We are on the road again and I am seeing intermittent service 4wd messages along with dtc p0700 tcm malfunction and sometimes I get the check engine light. Occasionally the cruise control will not engage and I see a p0500 speed sensor failure. Usually after a restart of two the cruise control will start working again. The lights on the three button 4wd shift panel usually shows 2wd but occasionally will show neutral, or 4wd or 4wd low even though the transfer case has not changed its setting. I hear no odd sounds or had any problems with the 4wd use this last winter.

I went to a big dealer here in Anchorage and the service writer said it could be three things, the tcm, the 3 button switch and I can't remember what the third is.

I am suspecting the tcm is the problem. The service writer called the tcm a transfer case control module but I always thought tcm meant a transmission control module.

In any case, can the tcm be easily replaced? Is there any programming that it needs which would require a dealer install it. I thought I might just get one online and try to r&r it myself. If that doesn't solve the problem I can then r&r the 3 button switch. I don't have confidence in most dealers ability to solve this kind of problem with any certainty and I don't want to pay their shop rates while they experiment.

Any info you've got would be appreciated.

[More Power]

I am suspecting the tcm is the problem. The service writer called the tcm a transfer case control module but I always thought tcm meant a transmission control module.

In any case, can the tcm be easily replaced? Is there any programming that it needs which would require a dealer install it. I thought I might just get one online and try to r&r it myself. If that doesn't solve the problem I can then r&r the 3 button switch. I don't have confidence in most dealers ability to solve this kind of problem with any certainty and I don't want to pay their shop rates while they experiment.


The TCM is the Transmission Control Module. The TCCM is the Transfer Case Control Module.

I installed a new TCCM in my Lil Red project truck, and it didn't need any dealer prep (programming). I've used a couple different TCMs in this truck, neither new, but they didn't need anything special.

The service manual outlines a complete testing process for the 4WD system, some steps using a Tech II Scan tool and some steps using a multimeter. Diagnostic labor at the dealership can be expensive if you're not equipped to do it yourself. Several here have replaced the pushbutton switch on the dash for a variety of problems. I did as well, for a weird pushbutton light problem on the switch panel. I didn't see any related trouble codes.

That said, since you're seeing a variety of seemingly unrelated trouble codes, I'd look for an electrical problem that could affect all systems - i.e. grounds, batteries, alternator, electrical/fuse panel corrosion, etc.

Jim