the roadie said:The PCM runs the dash lamp, and the TCCM runs the mode switch lights.
If you have NO sounds from either of the two motors, you may have other wiring issues. Have you downloaded the schematics and service manuals, and have some electrical troubleshooting experience?
the roadie said:That could be bad TCCM or wiring, or a double-failure of the actuator and encoder motor. A shop (not necessarily a dealer) with a high end scan tool can talk to the TCCM and command it to go through its paces.
Are you a DIY'er with some experience and a meter? Want to trace the schematics and see what you can find?
It could even be the switch, but a meter is the best way to troubleshoot that as well. Do the lights all flash when you first turn the ignition on, which is called the "lamp test" process?
Welcome! Glad you found us! As you've probably read, this is the classic symptom of a bad early version TCCM.toytooii said:Having some difficulty nailing down my issue. Hope I can get some advice here:
02 Trailblazer LTZ 135K miles.
Noticed indicator lights on selector switch were not showing at all and no shifting sounds from under the car..silence.
Pulled underhood fuse #8 for thirty seconds and reinstalled.
Restarted vehicle, all switch lights came on for two seconds then went out.
Service 4wd dash light illuminated.
Now, when starting, lights come on for two seconds then go out and service 4wd indicator remains illuminated.
The lamp test is a definitive check of a live TCCM. I thought the Service 4WD dash lamp would light up if the lamp test failed, but you obtained a dud TCCM IMHO. Where did you get it, and are you sure it's not another 2002, or from an AWD vehicle like the Bravada that runs the encoder motor but doesn't have the mode control switch? GOt any local buddies you can swap TCCMs with?What I've tried:
Replaced tccm with one believed to be ok. No lights at all on selector switch - not even at initial ignition but service 4wd indicator NOT illuminated.
Pulled underhood fuse #8 for 30 seconds: No effect
Put old tccm back in and suddenly every thing worked . ONCE! Now back to original issue.
Voltage at tccm appears to be present. I have a meter and willing to check deeper into this if I can get an idea of what to look for. I have schematics posted by The Roadie. Anything specific I should look for? Ignition on while testing? tccm attached while testing?
Encodor motor??? Selector switch??
the roadie said:Welcome! Glad you found us! As you've probably read, this is the classic symptom of a bad early version TCCM.The lamp test is a definitive check of a live TCCM. I thought the Service 4WD dash lamp would light up if the lamp test failed, but you obtained a dud TCCM IMHO. Where did you get it, and are you sure it's not another 2002, or from an AWD vehicle like the Bravada that runs the encoder motor but doesn't have the mode control switch? GOt any local buddies you can swap TCCMs with?
the roadie said:Welcome! Glad you found us! As you've probably read, this is the classic symptom of a bad early version TCCM.The lamp test is a definitive check of a live TCCM. I thought the Service 4WD dash lamp would light up if the lamp test failed, but you obtained a dud TCCM IMHO. Where did you get it, and are you sure it's not another 2002, or from an AWD vehicle like the Bravada that runs the encoder motor but doesn't have the mode control switch? GOt any local buddies you can swap TCCMs with?
Ascender has the true 4WD system with the switch and low range. It should be compatible. Bravada is not. Envoy is fine. I have one of those, and I don't go my kind of places without a working low range.toytooii said:...2005 Isuzu Ascender. ...
the roadie said:Ascender has the true 4WD system with the switch and low range. It should be compatible. Bravada is not. Envoy is fine. I have one of those, and I don't go my kind of places without a working low range.
the roadie said:Welcome! Glad you found us! As you've probably read, this is the classic symptom of a bad early version TCCM.The lamp test is a definitive check of a live TCCM. I thought the Service 4WD dash lamp would light up if the lamp test failed, but you obtained a dud TCCM IMHO. Where did you get it, and are you sure it's not another 2002, or from an AWD vehicle like the Bravada that runs the encoder motor but doesn't have the mode control switch? GOt any local buddies you can swap TCCMs with?
the roadie said:Ascender has the true 4WD system with the switch and low range. It should be compatible. Bravada is not. Envoy is fine. I have one of those, and I don't go my kind of places without a working low range.