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Codes 743, 753 Where to start?

I

Ice RHD

NAXJA Forum User
Location
NH
2000 xj rhd 4.0 aw4

I have codes 743 and 753.

I cleared the codes but after 5 min. of driving they came back. As soon as they came back it wouldn't shift properly but it would drive if it shifted it manually. Is it dangerous to drive it that way? Is there any way to test the solenoids or circuits in the car? Where should I start the diagnosis?
 
All I can give you is this .....

743 Torque converter clutch (part throttle unlock) solenoid circuit problem - shift solenoid C electrical fault

753 Overdrive solenoid control circuit problem (transmission relay circuit in Jeep RE transmissions.)

Maybe that can get you started?
 
Ice RHD said:
2000 xj rhd 4.0 aw4

I have codes 743 and 753.
Click to expand...

As part of good practice when listing codes, please quote the entire code number - it helps with accuracy by cutting down on guesswork. Thanks.

I cleared the codes but after 5 min. of driving they came back. As soon as they came back it wouldn't shift properly but it would drive if it shifted it manually. Is it dangerous to drive it that way? Is there any way to test the solenoids or circuits in the car? Where should I start the diagnosis?
Click to expand...

P0743: Torque Converter Clutch Solenoid/Trans Relay Circuits
P0753: Trans 3-4 Shift Sol/Trans Relay Circuits

Sounds like possibly a blown TCM. Try this: unplug the TCM and see if the shift behaviour stays the same. If it does, swap for a known-good one. Also check for damaged wiring to/from the TCM and transmission.
 
casm said:
As part of good practice when listing codes, please quote the entire code number - it helps with accuracy by cutting down on guesswork. Thanks.



P0743: Torque Converter Clutch Solenoid/Trans Relay Circuits
P0753: Trans 3-4 Shift Sol/Trans Relay Circuits

Sounds like possibly a blown TCM. Try this: unplug the TCM and see if the shift behaviour stays the same. If it doesn't, swap for a known-good one. Also check for damaged wiring to/from the TCM and transmission.
Click to expand...

Casm, is that what you meant?
 
joe_peters said:
Casm, is that what you meant?
Click to expand...

Ooops... Yep, that's what I was trying to say. Thanks for pointing that one out; totally slipped by me.
 
Could you elaborate on the term "behavior".

So the tranny wasn't shifting properly, now after I unplugged the TCM, it doesn't shift at all (automatically). There wouldn't be any behavior, correct?

I looked at the wiring quickly and dind't see any damage, but there might be some hidden in the harness some where. Some of the wiring looks pretty cramped between the engine and the firewall with tight bends and possibly pinched spots. I don't know if it's just the design of the RHD routing, it doesn't look like it was planned out properly.
 
I drove it again today.

It shifted ok for half an hour or so then started to bog, sputter and stalled a few times. I unplugged the tcm and drove manually for a while it was still bogging and sputtering but less. It seems to run better when cold. Also with the TCM plugged in it seems to run better if I keep it in 3rd gear and not D.
 
Did you check your throttle position sensor? It's located right behind the throttle body.

That can affect your timing on transmission shifts.
 
I drove it for the last two days and it seems to run better in cold weather. I was also thinking the tps could be screwing things up. The couple times it ran rough i slowed down and put it N before it stalled but even in neutral it ran badly. So I'm thinking something more could be going on than just solenoids ,TCM and wiring. The TPS sounds like it could be messing things up.
 
Also it wants to up shift to early. It seems to be shifting 1st, 2nd normal, skips 3rd and goes to 4th, TC lock to early. Some times as soon as 35mph
 
Test your TPS, it is non-adjustable so if out of spec replace it.

When you unplug the TCU and drive shifting manually you get 1st gear in 1-2; 3rd gear in 3; 4th gear in D; reverse, neutral, and park.
 
Haven't tested the TPS yet. But I drove it to work today and noticed in N it will rev inconstantly down to about 500 rpm and died once. I'm going to test the TPS right now.
 
I'm having difficulties back probing the connector and I think the batteries in my meter are low so no reading from the TPS yet.

Couldn't the VSS also be causing shifting issues?
 
TPS measures .8 smoothly up to 4.40 at WOT, that is if i measured it correctly. Is that in spec?
 
That is in Spec. (.26 to 4.49)

from the fsm...
The PCM supplies approximately 5 volts to the TPS. The TPS output voltage (input signal to the PCM) represents the throttle blade position. The PCM receives an input signal voltage from the TPS. This will vary in an approximate range of from .26
volts at minimum throttle opening (idle), to 4.49 volts at wide open throttle.​
 
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