There appears to be quite a lot of of an enig to more recent folks once their 4x4 attributes stop working. Due to the fact that crappy weather season is upon united state a many of human being are trying your 4WD features for the an initial time this year... And discovering every isn"t together it should be.Here"s my attempt at a troubleshooting checklist/flowchart. Hope this helps folks get a take care of on what"s wrong v their setup and how to solve it.Information in this thread applies to GMT360/370 trucks through selectable 4WD attributes (TrailBlazers, Envoys, Ascenders?). Trucks through non-selectable AWD (Rainiers, 9-7s, Bravadas) may discover some the the information below useful. But AWD trucks lack some that the parts disputed here.On come the show.Gah! mine 4WD doesn"t work! What carry out I do?Is the company 4WD irradiate on?Yes: go to section 1.

You are watching: 2002 gmc envoy service 4wd light

No: go to section 2.Section 1: My service 4WD light is on.Are there any type of lights lit top top the 4x4 selector switch?Yes: go to ar 2.No: try these steps.With the ignition off, turn the 4x4 selector move from left (2HI) to ideal (4LO) and earlier again about 20-30 times. With lack of use, the contacts inside the 4x4 selector switch can get a irradiate amount that oxidation on them. Repeatedly rotating the switch can sometimes clear this trouble up. If this doesn"t help, check out step 2. If action 2 doesn"t work-related for you, change your 4x4 selector switch. If instead of the 4x4 selector move doesn"t occupational for you, shot to find a neighborhood member through a proved working TCCM to swap in. If the trouble goes away, return her friend"s TCCM and buy a replacement because that yourself. Find these forums for replacement instructions.On some 2002 version year trucks, the Transfer instance Control Module (TCCM) have the right to have problem waking up when the engine computer system tries to speak to it. Fuse #8 in the engine just fuse block offers power to the TCCM. Pulling this fuse and replacing that will typically wake the TCCM up and allow the usage of 4WD because that a time. Resolving this needs either a dealer software application update (can be spendy, doesn"t always work) or instead of the TCCM through a unit native a 2003 or newer version with selectable 4WD.Section 2: Checking the motors.With the ignition on, switch the 4x4 selector move from 2HI come 4HI. You have to hear two distinct mechanical whirring sounds. One from the center of the truck (under you) and one native the former of the truck.I hear both whirring sounds: walk to section 3.I don"t hear the sound indigenous under me: there is an problem with the Transfer instance Encoder Motor. Check the connector going come the motor(cylinder looking thing) on the transfer instance for damage/corrosion. The motor might require replacement.I don"t hear the sound from the front: There is an issue with the prior Axle Disconnect Actuator. That is plugged into the front Axle Disconnect (AKA Splined Disconnect) located under the truck on the ideal side of the oil pan. Inspect the connector attached to it for damage/corrosion. If the connector is OK, change the actuator.Section 3: Identifying mechanically failures.Turn the ignition on however don"t begin the truck. Ar the 4x4 selector move in 4HI. Using a jack/jackstand raise the LEFT former wheel turn off the ground. Shot to turn that wheel by hand.The wheel walk not turn freely: That"s the expected behavior. The wheel will certainly be impede from turning by the passenger side tires being on the ground, and also the transfer situation connecting former to ago and the rear tires top top the ground.The wheel transforms freely: Crawl under the van so that you have the right to see the former driveshaft. Have actually an assistant rotate the left prior wheel by hand. Have the right to you see the driveshaft turn? If so, you have actually an interior transfer instance failure. Most likely because of worn the end clutches. If not, check out on.

See more: How Many Calories Does Mole Have, Calories In Dona Maria Mole, Mexican Condiment

It is likely your prior Axle Disconnect is no engaging properly. This have the right to be resulted in by worn bearings or a broken transition fork. Girlfriend can inspect for worn bearings by grabbing the inner tripot joint(closest to the former Axle Disconnect) that the best side axle and trying to wiggle it. Movement shows worn bearings. Also if her bearings aren"t overly worn, over there is a opportunity of a broken shift fork, spring, or other components. There is a good guide on the teardown and also rebuilding of the former Axle Disconnect here: http://www.offroadtb.com/articles/te...4wd-disconnect over there is an alternate method of addressing the transition fork problem here: OffRoad TB - watch topic - former axle disconnect fix... With a twist.If friend rebuild/replace your Front Axle Disconnect or room 100% sure it is work properly and still are at this point in the troubleshooting guide, girlfriend may have an interior front differential fail (likely) or broken intermediate pillar (extremely rare, couldn"t uncover an instance of this by searching). Currently is the time to do a write-up detailing every the measures you adhered to in this guide and any other monitorings made.There you have it. I hope this overview points girlfriend in the ideal direction.Additions/corrections welcome!
http://altoalsimce.org/image.php?type=sigpic&userid=49&dateline=1322008192 Wheel it...
Build thread ~ Youtube