DTC P0708 Set in the Transmission Control Module

Some 2020 CT4, Camaro, Escalade, Tahoe, Suburban, Yukon, Silverado 1500, Sierra 1500, Express, and Savana models equipped with an 8L45, 8L90, 10L60, 10L80, or 10L90 automatic transmission (RPO M5M, MF6, MI1, MI2, MI4, M5U, MQD, MQB, MQE) may have an illuminated Check Engine MIL and DTC P0708 (Transmission Range Sensor 1 Circuit High Voltage) set in the Transmission Control Module (TCM).

If these conditions are present, ask the customer if the engine has been cranking slowly or not cranking at all while attempting to start the vehicle. In addition, review the freeze frame data in GDS2 for DTC P0708 to determine if the system voltage was low when the code set.

If the system voltage was low in the freeze frame data or there is a concern with starting the vehicle, charge the battery and perform a battery test. If the battery fails the battery test, replace the battery, clear the DTC and test drive the vehicle. If the code does not reset, no further repairs are needed.

If no concerns were found with the battery, monitor the transmission range sensor data range, which should read between 7 and 93 percent. After driving the vehicle to get the transmission fluid temperature up to operating temperature, check to see if the transmission range sensor reading is between 7 and 93 percent.

If the transmission range sensor reading is not between 7 and 93 percent, disconnect and reconnect the pass through to engine harness connector. If the condition returns after reconnecting, replace the transmission pass through internal harness. (Fig. 17)



– Thanks to Terry Neuendorf and Mark Gordon

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One Comment

  1. Chad Roberts says:

    If we are doing the work to disconnect and reconnect, then seeing if it went away or is still present, why wouldn’t we just replace it the first time in? It’s hard enough getting paid for diag like this, then have to do the physical job twice? How do will bill and get paid for that? Will diag olh after the initial hour be approved? the harness pays 1.7 I think. with 1.0 diag. But we may have to go in twice.

    What if it returns after the D&R procedure appears to work and the vehicle comes back? Is it now a repeat repair blamed on the dealer or technician?

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