Hi everyone. I bought a Jeep with an electrical issue that has spent the last few years being worked on with no solution.
With the Jeep cold and started up at idle, 30 minutes later at running temp, the fan roars at high rpm and the dash lights up with multiple illuminated icons including "hot oil".
At this point the Jeep is in limp mode and needs a few hours to cool down and reset.
The lights flicker, they aren't solid. Transmission is not hot.
Parts previously replaced: TIPM, ECU, fan, engine harness. Transfluid flush.
My diagnosis so far.
I have been working on this in the evening after work. If I pull the relay out for the TCM the exact lights come up on the dash including "hotoil". The difference the lights don't flicker, they are solidly lit. Swapped relay with low fan speed. No change.
With the lights flickering it's like the heat in the engine bay is creating resistance somewhere. Noted.
I have gathered baseline data when cold and not faulting. Power to TCM "yellow red stripe wire" 12.6 V static, 14 V when running, 13.6 V when faulting.
Earth the TCM 0.6 ohms when not faulting, 0.6 ohms when faulting.
Can wires to TCM whi/blu and whi/grn 61.2 ohms not faulting, 200ohms faulting.
So something is creating a fault on the can bus when the vehicle is at running temp.
Next diagnosis.
Ohms reading for both can wires below 1 ohm from TCM to multi pin connector under battery box at firewall, firewall connector to TIPM, TIPM to multi pin connector at radiator. For Australia its RHS under the power steering reservoir.
Also 60 to 62 ohms between all those connectors when not faulting.
Tonight the next step is to run the vehicle until it faults, disconnect all the Main connectors and retest resistance of individual can wires and as pairs.
Any thoughts would be greatly welcome
With the Jeep cold and started up at idle, 30 minutes later at running temp, the fan roars at high rpm and the dash lights up with multiple illuminated icons including "hot oil".
At this point the Jeep is in limp mode and needs a few hours to cool down and reset.
The lights flicker, they aren't solid. Transmission is not hot.
Parts previously replaced: TIPM, ECU, fan, engine harness. Transfluid flush.
My diagnosis so far.
I have been working on this in the evening after work. If I pull the relay out for the TCM the exact lights come up on the dash including "hotoil". The difference the lights don't flicker, they are solidly lit. Swapped relay with low fan speed. No change.
With the lights flickering it's like the heat in the engine bay is creating resistance somewhere. Noted.
I have gathered baseline data when cold and not faulting. Power to TCM "yellow red stripe wire" 12.6 V static, 14 V when running, 13.6 V when faulting.
Earth the TCM 0.6 ohms when not faulting, 0.6 ohms when faulting.
Can wires to TCM whi/blu and whi/grn 61.2 ohms not faulting, 200ohms faulting.
So something is creating a fault on the can bus when the vehicle is at running temp.
Next diagnosis.
Ohms reading for both can wires below 1 ohm from TCM to multi pin connector under battery box at firewall, firewall connector to TIPM, TIPM to multi pin connector at radiator. For Australia its RHS under the power steering reservoir.
Also 60 to 62 ohms between all those connectors when not faulting.
Tonight the next step is to run the vehicle until it faults, disconnect all the Main connectors and retest resistance of individual can wires and as pairs.
Any thoughts would be greatly welcome
