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98 trans slips in drive not in 1st gear

J

javelin401

NAXJA Forum User
Location
South Carolina
Wife talking sell now,:passgas: so you know its serious. Intermittent issue, slippage in 1st gear in drive, hooks right up selecting 1,2 range. engine light on, throwing 3 solenoid codes (p0753 shift sole A, p0758 shift sole B, p0743 torque converter clutch sole circuit). When it shifts normal, engine light shuts off after a toggle (run/off/run) session and lights again when she starts slipping. All 3 soles ohm good when I had the pan down. Trans mechanic wont take my money, says its an electrical issue. This began shortly after a trans pull for a flex plate swap but all connections look good. Maybe a TCM or wiring issue, Next move: ohm solenoids from the TCM connector pinouts. I have the FSM to help.
I have researched past related threads but they are aged (transonline site 4sale) The throttle position sensor is properly adjusted, new neutral safety sw. Ive been cleaning grounds as ive been going thru this restore since July and its getting frustrating as f here. AW4 4WD
thanks for any help folks!
 
Throwing all those codes points to some sort of voltage issue. BTW there is no adjustment on the tps, did you mean tv cable? Out of spec tps will cause all sorts of weird shifting issues but I dont know what kind of codes they will cause to trip. Mine is a 95 and won't even trip a code with a rod sticking out of the block.
 
With the history of this Jeep and you doing a trans install 3 times I would say you have a lot of sensor/wiring to check!
 
The most recent repairs or modifications should always be the first suspect. As suggested, the related wire harnesses and wire plugs should be carefully inspected for damaged wires, and bent/pushed back wire plug pins.



P0753 JEEP Possible Causes

Low transmission fluid level
Dirty transmission fluid
Faulty shift solenoid valve
Shift solenoid valve harness or connectors
Shift solenoid valve circuit is open or shorted
 
javelin401 said:
Next move: ohm solenoids from the TCM connector pinouts. I have the FSM to help.
Click to expand...

I agree, it's gotta be wiring and not the trans itself. There is also a connector under the hood, against the passenger side firewall. Clean and measure from there as well. Check that the wiring didn't get pinched between the bellhousing and engine block when you reinstalled the trans.
 
Unclewolverine said:
Throwing all those codes points to some sort of voltage issue. BTW there is no adjustment on the tps, did you mean tv cable? Out of spec tps will cause all sorts of weird shifting issues but I dont know what kind of codes they will cause to trip. Mine is a 95 and won't even trip a code with a rod sticking out of the block.
Click to expand...
 
thanks All! Agreed check cabling for sure, nothing pinched but could have mashed something.
BTW there is no adjustment on the tps said:
there is a tranny throttle cable adjustment, its up on the valve cover, 98 FSM is wrong on this point, does effect shift quality, harsh vs softer shifting but would not create this issue. I will endeavor over the w/e
Peace
guess i aint figured out the quote thing so much
Click to expand...
 
My 2000 FSM calls it a "transmission throttle cable, my AW-4 FSM calls it the "throttle pressure control".
 
I once called it a detent cable here and was told on jeeps it was called a throttle valve cable. Many names same function, I just want to make sure your weren't trying to adjust the throttle position sensor on he throttle body because that is non adjustable and easily fails.
 
Lots of people incorrectly call it a kickdown cable too, but unlike the older transmissions, the AW4 shifting is electronically controlled. It controls the hydraulic pressure in the transmission, making shifting firmer/faster when more throttle is applied. When misadjusted you can get harsh shifting, or soft lazy shifting or even no shifting at all.

Just to confuse things even more, the TPS on the older Renix jeeps were slotted and adjustable. Not on a 98 though.
 
Sidetracked on more "fixable" priorities, I'm back, frustrated as ever. Still working off the premise that something was disturbed with the 2x trans removal flexplate replacement. Ohm'd the 3 solenoids, this time thru the harness at the firewall. All 13 ohms to ground and they all pulled about 1 amp when I juiced each one individually. Checked the rest of cabling from the trans. I find 2 speed sensors not including the vehicle speed one. FSM mentions only one in trans diagnostics but shows 2 in the schematic! (a front and rear sensor)
I get a good pulsing reading on meter from both of these (rear wheels off the ground for the rear sensor). Cleaned corrosion from the transfer case switch and the 2 pin plug. I think its bad with high resistance 4 - 15 Meg ohm actuated and not actuated. I doubt it can cause this shifting issue?
I am wondering where C107 connector is physically located? as it is involved in much of the signals from the TCM.
Still somewhat intermittent, the issue only occurs when vehicle warms up. I'm forced to shotgun at this point, maybe different TCM or change out all the solenoids? :banghead:
 
C107 is at the firewall/rear of the valve cover.
 
The description on the codes says electrical, although I think the 98+ can also tell when they're in the wrong gear by comparing the input versus output speeds (input speed sensor was added in 98, btw). Have you ohm'd out the solenoids from the TCM connector itself?

It's rare, but throwing codes for all three solenoids which measure good would make me suspect the TCM is bad. Is it applying 12-volts to the #1 solenoid with key on, which should be commanding 1st gear?

Fluid level is good right? Just checking as someone else around hear chased a similar issue and it was just very low on fluid. More spitballing, but wiring harness didn't get pinched in between the bellhousing and engine? Shifting manually makes me think it's good mechanically. Cooler lines not kinked?

qJ49jWt
 
Try this test. It may help narrow things down for you. (From a 2000 FSM.)

MANUAL SHIFTING TEST
(1) This test determines if problem is related to
mechanical or electrical component.
(2) Stop engine and disconnect transmission control module or module fuse.
(3) Road test vehicle. Shift transmission into each
gear range. Transmission should operate as follows:
• lock in Park
• back up in Reverse
• not move in Neutral
• provide first gear only with shift lever in 1–2
position
• operate in third gear only with shift lever in 3
position
• operate in overdrive fourth gear in D position
(4) If transmission operates as described, proceed
to next step. However, if forward gear ranges were
difficult to distinguish (all feel the same), or vehicle
would not back up, refer to diagnosis charts. Do not
perform stall or time lag tests.

CAUTION: Do not over speed the engine during the next test step. Ease off the throttle and allow the vehicle to slow before downshifting.

(5) Continue road test. Manually downshift transmission from D to 3, and from 3 to 1–2 position.
Then manually upshift transmission through forward ranges again.
(6) If transmission operation is OK, perform stall, time lag and pressure tests. If transmission shifting problem is encountered, refer to diagnosis charts.
(7) If a problem still exists, continue testing with DRB scan tool.

This same manual states C107 is a black connector at the rear of the engine compartment. You can see it on the right side of the diagram here.

unknown.png
 
lawsoncl said:
The description on the codes says electrical, although I think the 98+ can also tell when they're in the wrong gear by comparing the input versus output speeds (input speed sensor was added in 98, btw). Have you ohm'd out the solenoids from the TCM connector itself?

It's rare, but throwing codes for all three solenoids which measure good would make me suspect the TCM is bad. Is it applying 12-volts to the #1 solenoid with key on, which should be commanding 1st gear?

Fluid level is good right? Just checking as someone else around hear chased a similar issue and it was just very low on fluid. More spitballing, but wiring harness didn't get pinched in between the bellhousing and engine? Shifting manually makes me think it's good mechanically. Cooler lines not kinked?

qJ49jWt
Click to expand...

Yes I should check the solenoids back at the TCM and have to check voltage as you mentioned to solenoid #1 during the road test, cold vs hot. Level good, nothing pinched, kinked.
Also C107 looks fine. (didnt know the FSM has those locations shown)
thanks all !!
 
OK so road test while monitoring the TCM output to shift sole #1 (the 1-2 and 3-4 solenoid control per FSM) reveals much!!! I tapped off the module's pin #12 going to the white wire w/DVM. The AW4 does not like trying to start out in 2nd gear which is what testing shows, where 12v is being applied in Drive mode and she slips. Drop it into 1-2 and voltage cuts to zero, 1st gear is applied and off we go; hit 2nd gear and all good with voltage present until 3rd takes over and that solenoid is done with its job, no voltage in 3rd or OD. In decel: voltage reappears once it drops to 2nd but remains in second when stopped because the solenoid is still energized by the control.
Soooo this is either bad TCM or bad input signal to the TCM. I should probably take readings on the 2 speed sensor inputs at the TCM tho they tested good back at the connector (not referenced in the FSM schematic).
Heavy leaning TCM tho I'm still loving opinions here, maybe another input of importance is confusing the TCM?
 
javelin401 said:
the 1-2 and 3-4 solenoid control
Click to expand...

I don't know why the FSM labels it that way on the diagram because it's confusing. More simply, here's what the solenoids should be doing (and what your troubleshooting says the TCM is commanding?)

1st gear - Solenoid 1/A only
2nd gear - Both shift solenoids
3rd gear- Solenoid 2/B only
4th gear - neither is powered
 
Lawson, I wanted to post a photo of the FSM page, but file attachments not allowed, not sure why that is?? I assume you know what it reads anyway. Your solenoid list makes sense so I checked solenoid 2 and it's energized in all 7 gear ranges! I'm pretty sure OD was working so that part confuses but it is speaking loud to me that the TCM is bad. I also verified both speed inputs good at the TCM with pulsating meter readings.
thanks for the good info!!
 
javelin401 said:
Lawson, I wanted to post a photo of the FSM page, but file attachments not allowed, not sure why that is?? I assume you know what it reads anyway. Your solenoid list makes sense so I checked solenoid 2 and it's energized in all 7 gear ranges! I'm pretty sure OD was working so that part confuses but it is speaking loud to me that the TCM is bad. I also verified both speed inputs good at the TCM with pulsating meter readings.
thanks for the good info!!
Click to expand...

Yeah, I have the FSM. Actually I do know why they label it that way, and it's because of how the solenoids cause the gear selection in the valve body. If you're getting power to solenoid #2 when not moving, I would suspect the TCM is bad.
 
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