AW4 Overdrive question

[Akula69]

Basically, just what the title says.

 

The 2000 AW4 in Junior is misbehaving...throwing the P705 code which translates into the OD solenoid is not 'electrically' checking out upon start. I have replaced the solenoid and it worked for awhile but now has started to throw the code again.

The problem is the OD works occasionally and has no pattern to its misbehavior. Over the weekend the truck was driven to Hattiesburg and back - OD worked on the way up and did not on the way back (which would seem to indicate fluid circulation and/or warm up is not the case). When the solenoid was replaced the filter and fluid was changed out - no particular debris or dirt was observed (filter and fluid had been changed when the trans was installed at conversion).

 

Because the solenoid is mechanical (activated by an electrical signal) can the TCM be the culprit here? When the truck is started, does the TCM physically actuate the solenoid or just check to see if it worked the last time the truck was running?

 

Thanks

 

Jake

[HOrnbrod]

I love intermittent electrical problems. NOT!

 

Do you have an electrical FSM for your 2000 XJ? if so, I'd check for continuity (~14 ohms) from the TCU connector through the TC lockup solenoid coil using the electrical FSM for the correct pinouts. This will verify your wiring is good.

 

Aftermarket AW4 solenoids are usually junk - lots of intermittent "no-workie" reports around.

 

A bad TPS can also cause intermittent TCU lockup and/or shifting. Also the signal from the brake pedal to lock/unlock the TCU solenoid may not be getting there or is intermittent. Check the adjustment of this switch.

 

Just throwing things out Jake.

 

Good thread here:  http://www.naxja.org/forum/showthread.php?t=1125276

 

Good 2000 XJ TCU here if needed:  http://www.ebay.com/itm/56041386AB-Jeep-Cherokee-Transmission-Computer-Control-Module-TCM-TCU-1999-2001-/151828161242?fits=Model%3ACherokee&hash=item2359a9e2da:m:mJ_m-kGfvETtAtLDtpnnaKw&vxp=mtr

[Akula69]

Thanks for the input Don.

 

Yeah, I've heard about the aftermarket sensor issues - actually had them with this MJ on the TPS and the CKP....had to lay out the $$$ for the mopar sensors.... :doh: Did use the ohmmeter on the harness (forgot to mention that in the original post) and was getting approximately 12.9 ~ 13.6 on the scale (which would seem to indicate good..?) One of the posters in the thread talked about the torque converter itself...but if that was weak or malfunctioning I imagine the other transmission actions would reflect that.

[HOrnbrod]

The ohms reading indicates the solenoid coil is okay, but doesn't mean it's making/breaking every time. As you of course know.  :yes:  And yes, I think a bad TC would most likely cause other shifting issues. 

 

Did you replace the TC solenoid with a Mopar part?

 

Do you have a tranny cooler on the 2000 AW4? I remember years ago I had rare intermittent TC lockup issues on real hot days, but it never happened again after I plumbed in a factory cooler.

[Eagle]

I don't know how the overdrive solenoid would be linked to the torque converter. OD is a fourth gear in the transmission, it's not the torque converter lock-up (which also operates in third gear).

[Akula69]

Eagle, on 25 Jul 2016 - 12:04 PM, said:

I don't know how the overdrive solenoid would be linked to the torque converter. OD is a fourth gear in the transmission, it's not the torque converter lock-up (which also operates in third gear).

I'm with you on this one, but I figured mentioning the other poster's comment might spark some additional thoughts. AFAIK, the torque converter is simply a fluid coupling...but it does affect pressure. I've never known anyone who has experienced a bad one (kinda one of those parts that hangs on forever).

I do have an older (small)  trans cooler on this rig and did replace the OD solenoid with a mopar part. if all else fails I suppose I could try a larger cooler.

[cruiser54]

Have you checked out the connectors by the trans dipstick? One gray ond one black. Usually fairly corroded inside for some reason. They're the information superhighway for TCU signals. 

[HOrnbrod]

 

Eagle, on 25 Jul 2016 - 12:04 PM, said:

I don't know how the overdrive solenoid would be linked to the torque converter. OD is a fourth gear in the transmission, it's not the torque converter lock-up (which also operates in third gear).

I'm with you on this one, but I figured mentioning the other poster's comment might spark some additional thoughts. AFAIK, the torque converter is simply a fluid coupling...but it does affect pressure. I've never known anyone who has experienced a bad one (kinda one of those parts that hangs on forever).

I do have an older (small)  trans cooler on this rig and did replace the OD solenoid with a mopar part. if all else fails I suppose I could try a larger cooler.

 

True, the torque converter lockup solenoid is applied in all the forward gears, so it shouldn't affect only OD if it was defective. BUT I have read of several cases online that replacing the TC lockup solenoid cured a no OD problem.

 

A dirty/defective NSS has also been known to cause a no OD condition since the TCU signals go through it using different contacts for the 1-2-3-OD drive gears. Taking it apart and cleaning it up might help.

 

http://gojeep.willyshotrod.com/HowtoNSSrebuild.htm

[Akula69]

cruiser54, on 26 Jul 2016 - 08:43 AM, said:

Have you checked out the connectors by the trans dipstick? One gray ond one black. Usually fairly corroded inside for some reason. They're the information superhighway for TCU signals. 

I always take your advice! When my son and I converted Junior we cleaned and checked these and every other connector (unlike when we did his and chased a 'no bus' condition around for awhile....)

[75sv1]

^{I had my battle with an 98 last year. I did use after market solenoids. They did work, but I didn't run the vehicle that long. Sold it a few months latter. My problem was one of the speed sensors, the out put one. Not fun to change. The latter AW4 , aqua colored solenoids are suppose to be the best. There are a lot of sensors in the 'loop'. Don't know which one or all of them that would effect the OD. Since intermittent, unplugging the  TCU, might not show if its the trans or the electrical components. Even the brake light switch has some input on the trans function. Also the TBS. Might check both of those. Also, adjust the trans cable. Easy to do.}

[Akula69]

OK - after replacing all three solonoids the old transmission feels like new again! So far (approx. 100 miles), the codes have not returned and the transmission is shifting crisply in all gears. 

 

Thanks for all the help!

 

Jake

[cruiser54]

Thanks for the update.