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Encoder Motor Problem for 97 GMC Jimmy

40 messages,  Last post on Oct 26, 2009 at 4:26 PM

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#21 of 40 Re: Stuck in 4 wheel high puzzler [dougaroo] by repairdog Dec 12, 2006 (2:55 am)
Replying to: dougaroo (Dec 11, 2006 7:49 pm) Points to vac applied to the front actuator so with the vehicle running pull that vac hose off the solenoid on the firewall and see if you hear the actuator release - if so put a golf T in the source side and test it out - can leave till buy a new one but no 4wd. Those solenoids leak - internally sometimes applying vac or externally for slow engagement. Replies to this message: dougaroo (Dec 15, 2006 11:21 am) s10468 (Dec 20, 2006 2:08 pm) bruce48532 (Dec 15, 2006 3:43 pm) repairdog (Dec 17, 2006 4:22 am)
#22 of 40 Re: Stuck in 4 wheel high puzzler [repairdog] by dougaroo Dec 15, 2006 (11:21 am)
Replying to: repairdog (Dec 12, 2006 2:55 am) Bought a new actuator valve. No change. Still stuck in four high. With a vacuum pump checked the actuator (under the battery) and it holds a good (20psi)vacuum. I by passed the valve and hooked the two hoses together and it puts it in four wheel high. Plug the vac hose and it drops into 2wheel. So by deduction it appears voltage from somewhere is keeping the actuator valve open. When I pull the fuse this of course cuts the voltage to the actuator valve. Any suggestions on where to look now? Replies to this message: s10468 (Dec 20, 2006 2:08 pm)
#23 of 40 1999 GMC 2500 4WD Problem by bruce48532 Dec 15, 2006 (3:43 pm)
Replying to: repairdog (Dec 12, 2006 2:55 am) Error code: 0323 T-Case Lock Circuit Low Parts Repaced: Dash Switch and 4WD Frt Axle Actuator   Current Symptoms: 1. Defaults to 4HI after I switch the ignition on 5 sec off 5 sec then on 10 sec.,will also switch to Auto 4WD. 2. Depressing dash buttons runs 4WD Frt Axle Actuator with whining then vibrating grinding noise at end of cycle. Acts like the actuator is trying to shift gears but overloads, then shuts down when trying to switch to 2Hi or 4Low.   I Checked fuses, left side drivers door and ATV under hood, OK.   Low Fluid level possible ? Replies to this message: repairdog (Dec 17, 2006 4:22 am)
#24 of 40 Re: 1999 GMC 2500 4WD Problem [bruce48532] by repairdog Dec 17, 2006 (4:22 am)
Replying to: bruce48532 (Dec 15, 2006 3:43 pm) Looks like an NP246 case (larger than 236 auto case) but should work the same. Sounds like one of the ball type sensor switches on either the front axle or transfer is stuck ON (ball pressed in) so the TCCM thinks its 4wd time. Ckeck them and if OK standand trick is pull the power for 30 min and see if it reboots. Also pull and plug the vac line on the firewall solenoid and see if it stays in 2wd then, if so replace solenoid. Check the connectors and wiring down on the transfer case too - cuts or bare spots.
#25 of 40 Re: Stuck in 4 wheel high puzzler [dougaroo] by s10468 Dec 20, 2006 (2:08 pm)
Replying to: dougaroo (Dec 15, 2006 11:21 am) Dougaroo,I also own a 99 s10 and my blazer is behaving exactly the same as yours is. The encoder/motor buzzes and will not complete the shift back to 2HI. I replaced some vacuum line and the frt axle clutch solenoid(actuator valve)... still not fixed. Were you able to solve anything yet?
#26 of 40 Stuck in 4 wheel High puzzler by dougaroo Dec 26, 2006 (5:42 am)
No I have not solved the problem yet , but was able to find a possible fix from another posting a I made.   Here's the text of the post and the link   http://www.automotiveforums.com/vbulletin/showthread.php?p=4521487#post4521487    EUREKA!!!!!! Found the Problem with the Blazer. After testing all of the components involved with the 4 wheel system I couldn't find any problems... I finally decided to pull the encoder motor to see if I could shift it manuals to make sure I didn't have a mechanical problem and found the problem. Looking at the encoder motor from underneath It looked almost new. I pulled it off and found a major build up of corrosion between the plastic gasket and the motor gearbox. So much so it distorted the gearbox and bound up the unit so it wouldn't complete the shift. I scraped all the corrosion off and it had a very pronounced bow to the unit. I pulled it all apart ( I'd like to kick the engineer that decided to put security torx bolts in the cover) and separated the 2 halfs. I checked the machined surfaces with a straight edge and found that the housing was warped by at least 3/16th of an inch. I figured nothing ventured nothing gained so I pulled the unit completely apart and using a press straightened the 2 halfs the best I could. I then used a big mill file and flattened the two halfs so they were true. While I had the unit apart i checked the brake unit on the end of the motor and it was fine except that there was some gunk on the friction plate so I cleaned it off. I checked the motor and found one of the stabs for the power feed was almost burnt off. I cleared away some of the insulation and soldered the wires directly to the motor feed wires. No chance to loose continuity again. I reassembled the unit and installed it back on the transfer case, installed the driveshaft and lowered the truck to check the shift modual connections. After connecting the modual I replaced the fuses and started the truck. Bingo the truck snapped into 2HI and works like a champ now.. Sorry for the long post but thought you guys would like to have the info.
#28 of 40 2000 Jimmy 4WD probs by groundhog03235 Dec 29, 2006 (8:46 am)
Hi guys! We have a 2000 Jimmy approx 98k miles. Last winter the 4WD was perfect, this year nothing-when I push the buttons for 4 high or low or the auto 4 high, the light blinks for awhile and then goes right back to 2 high. Took it to the local GM dealer to be checked-they condemned the encoder motor. I'm going to try disconnecting the battery as previously suggested-if that doesn't work, could it be time for a new motor? Replies to this message: repairdog (Dec 30, 2006 5:24 am) groundhog03235 (Dec 31, 2006 8:22 am)
#29 of 40 Re: 2000 Jimmy 4WD probs [groundhog03235] by repairdog Dec 30, 2006 (5:24 am)
Replying to: groundhog03235 (Dec 29, 2006 8:46 am) Could be - have you done all the things listed to test all the other components yet and is it 3 or 4 button - vac to front actuator is often the reason. Replies to this message: groundhog03235 (Dec 31, 2006 8:22 am)
#30 of 40 Re: 2000 Jimmy 4WD probs [repairdog] by groundhog03235 Dec 31, 2006 (8:22 am)
Replying to: repairdog (Dec 30, 2006 5:24 am) I tried disconnecting the battery-no luck there. So I consulted my local mechanic who suggested that we try the new motor based on the dealer's diag. I was able to get it at his cost (still $470!) and it did the trick. But I appreciate the other info for future reference.

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