Had an odd thing happen the other day, thought I'd bounce it off my friends here, get your thoughts.

The truck has been perfect for months, zero issues. Yesterday, over the course of 20 mins and three starts of the truck, after a few seconds of on time, the '4wd Service' light came on and there was no position indicator on my AWD switch (usually at AWD). Also... at the same time, the 'Security' light came on solid. I got where I was going in the 20 mins and it parked for 3 hours.

After starting again, the lights came back, but 5 mins later while driving home, they both went out and the AWD switch indicator was back. When I got home a few mins later, I cycled the 4wd through AWD/4HI/4LO and it all worked fine. Anything come to mind? I have not driven it since then.

 

That is odd. To me that is all one related issue, I have a good ole' lever for my 4wd so I don't know what could be messing with that and the security. If I remember correctly though there is a module on those newer one that will recognize the key for the security system. Usually though they won't start then.

 

The 1st post was a Sat drive. It was parked Sun (was busy, didn't look into it more). Yesterday (Mon) it did the same thing, two lights on for a 10 min drive to pick up a friend, then after leaving there and driving for another 5 mins they went out, back to normal.

A new oddity... 5 mins after the lights went back to normal, the chime binged maybe 8 times saying 'look at the dash to see what light I just turned on', but there were no lights. After parking for 5 hours, all was normal for the drive back to the friends house and then me home.

Since security and 4wd are separate systems, I'm thinking this may be a do-over of what happened with my A/C. Last Oct I pulled the heads, major under-hood surgery. All was well after, but 6 mos later this spring the A/C quit. The A/C prob turned out to be a bad ground wire cluster lug that got buggered a bit from the engine work. I plan to dig around today to see if those two systems have any electrical things in common.

[EDIT: Per the FSM, the grounds relating to security and t-case control are under the dash, so not related to the motor work.]

[EDIT #2: I did more research and what I'm seeing is exactly pointing to a bad TCCM. I found the exact one on eBay for $65, pulled from an '03, should be here Sat. I'm usually a 'make 100% sure it the right part before spending money' guy, but this thing is such a pain to get to, and is hard to test since it's intermittent. ]

 

Did you connect your tuner to see if it shows any codes?

 

I did a code check, nothing. I read the FSM more, says that if there is no sig from the TCCM after 6 secs of power on, it throws the dash light for '4x4 svc'. Thats exactly what I was getting, a delay before the light.

FSM also said that all the dash lights for all possible D features are in the dash, even those for vehicle features not on that vehicle (I guess so only one dash panel p/n). When the battery is disconnected for long enough, the dash 're-learns' what features are on the vehicle and removes lights for not-installed features from the 'which bulbs to test when key first turned on' list.

Well, before knowing about the re-learn, I disconnected the battery for a bit to reset everything, hoping it would fix my problem. When I reconnected and did first key on, there was no '4wd svc' light with key on bulb test. Apparently a dead TCCM equals no t-case present on vehicle, so it 'learned' I had a 2wd model.

The new TCCM should be here tomorrow. I'm ignoring the 'security' light for now, hoping it's either unrelated or just a symptom of the bad TCCM on the PCI buss.

[PS: That friggin TCCM box is a PITA to get out! Old one is now sitting on my desk.]

 

Well, I got the new (used) TCCM and there is no change. I still don't get the 4x4svc light at bulb test, but I get a dash bong tone at the 6 second point (? same bong time as when the 4x4 light would come on) with no dash light. The only other related part (I think?) is the CTM which handles PCI signals. Anyone have ideas?

[EDIT: Dealer only wants $39.95 to run the DRBIII tool against it, see whats what. I have a 7:30AM appointment tomorrow (Sat).]
[EDIT#2, still Fri night. Put it together enough to go to dealer, and it's all perfect, no errors, no codes, 4x4 bulb shows on key-on-bulb-test, still using orig TCCM. All I did new since it didn't work was un/replug the CTM. It's frustrating enough though that I will still have the dealer throw a DRBIII on it tomorrow.]

 

Drove it 6 times since last night. Works fine, no errors, on all original parts. The only thing I could imagine is un/replugging the three CTM plugs did something. Took it to the dealer for the DRBIII test, zero issues. They did offer to flash it to the latest firmware, circa 2003, the one we call 'death flash'. I opted out.

So, I put the dash all back together and drove it again, still no issues. I have no idea other than CTM dirty plugs.

 

Hopefully that's it.

 

Nope, all symptoms came back to day, and all intermittent. If you run some errands and start it up 8 times to make a few stops...
= Sometimes the 'Svc4x4' light will come on.
= Sometimes the 'Security' light will come on.
= Sometimes you get no lights, just 4-10 random chimes with no lights, few seconds apart.
= Sometimes any of the above three will come at the same time.
= Sometimes you get nothing and all works fine.
= Always... everything else works fine, every gauge, all dash functions, all door ajar indications, vehicle drives normally.

 

How old is your battery? I would load test it, see if its shorted out internally. Quick voltage drops could be triggering some of these. The volt gauge in the dash won't pick up these drops, it doesn't respond fast enough. Seen weird issues with bad batteries around these parts......