Dealership charging way too much for 'transmission brain' and two other names ?

tclifford

Thank you, experts for all your help.
I have a 2007 Jeep Grand Cherokee that had the engine light coming on, and resulted in OBD codes
P0507 (Idle control system RPM too high) and P0710 (Transmission fluid temp too high).
I experienced no other symptoms, idle seemed fine, no problems accelerating or in shifting.
Tranny is automatic.
The dealership wants me to replace the 'transmission brain' (TCM) for $940 plus $500 labor.
Many posts seem to indicate faulty or shorted sensors, idle air valve, cleaning throttle body,
replacing power steering power switch, and others.
They say nothing about the TCM.
The dealership in its documentation also call the part 'connector elect 030', and 'valve body'.
It really seems I'm getting ripped off.
Has anyone else seen this particular issue, and what it turned out to be ?
I've already replaced the original engine with a Jasper rebuild (rocker-arms were working loose),
and would not like to repeat that with the transmission.

Thanks again.
repeat that w

Mr_Shiftright

There's no reason there should be any doubt about this. If the dealer did the proper testing, and he's right, then the PCM/TCM could very well be the problem. Here's how the testing goes, to eliminate things one by one.

Use a scan tool to monitor the transmission temperature sensor data parameter. Disconnect the TFT sensor; the scan tool value should drop to a very low value. Next, connect a jumper wire across the terminals. If the scan tool now displays a very high temperature, the connections are sound and the ECM can recognize the input. This means the problem is most like the sensor and not a circuit or PCM problem.

Test the sensor: Disconnect the transmission fluid temperature sensor connector. Next, measure the resistance between the two sensor terminals using a digital multimeter set to ohms. Start the engine and watch the meter value; the values should decrease smoothly as the engine warms up (check the engine temperature gauge on the dash to ensure the engine reaches operating temperature). If engine temperature increases but TFT resistance does not decrease, the sensor is faulty and should be replaced.

Check the circuit: Check the reference voltage side of the circuit: with the ignition on, use a digital multimeter set to volts to check for a 5-volt reference from the PCM at one of the two transmission fluid temperature sensor terminals. If no reference signal is present, connect the meter set to ohms (with the ignition off) between the reference voltage pin on the TFT and the reference voltage pin on the PCM. If the meter reads out of limits (OL) there is an open circuit between the PCM and sensor that will need to be located and repaired. If the meter reads a numeric value, there is continuity. If everything is good up to this point, you'll want to check that there is 5-volts coming out of the PCM at the reference voltage terminal. If there is not a 5-volt reference from the PCM, the PCM is probably faulty.