P0736

DTC P0736

Circuit Description
The transmission control module (TCM) calculates gear ratio based on data from the automatic transmission input speed sensor (AT ISS) and the automatic transmission output speed sensor (AT OSS). The TCM compares the known transmission gear ratio to a calculated ratio for each commanded gear.

If the TCM detects an incorrect reverse gear ratio, indicating excessive slip or drag within the transmission, then DTC P0736 sets. DTC P0736 is a type A DTC.

DTC Descriptor
This diagnostic procedure supports the following DTC:

DTC P0736 Incorrect Reverse Ratio

Conditions for Running the DTC
^ The engine speed is 400 RPM or greater.
^ No CAN DTC's U2104 or U0100.
^ The brake switch is released.
^ Trans. protection mode is OFF.
^ No TR switch DTC P0705.
^ No TFT DTCs P0711, P0712, or P0713.
^ No ISS DTC P0717.
^ No OSS DTC P0722.
^ No engine speed DTC P0727.
^ No TCC DTC P0741.
^ No solenoid DTCs P0962, P0963, P0966, P0967, P0970, P0971, P0973, P0974, P0976, P0977, P0979, P0980, P0982, P0985 or P0986.
^ No engine torque DTC P1781.
^ No throttle position DTC P1791.
^ The ignition voltage is 10.5-18 volts.
^ The engine run time is 5 seconds or greater.
^ The transmission temperature is 20°C (68°F) or greater.
^ The transmission is not in PARK or NEUTRAL.
^ The elapsed time since the most recent range change is 8 seconds or greater.
^ The output shaft speed (OSS) is 500 RPM or greater after shifting into reverse.

Conditions for Setting the DTC
The TCM commands reverse and the actual gear ratio is not within 2.54:1-3.81:1 for 6 seconds:

Action Taken When the DTC Sets
^ The TCM requests the powertrain control module (PCM) to illuminate the malfunction indicator lamp (MIL).
^ The TCM turns the Trans. Protection Mode ON.
^ The transmission will operate in 5th gear when the transmission is shifted into D or I range and 2nd gear when shifted into L range.
^ The line pressure is at maximum.
^ The torque converter clutch (TCC) is disabled.
^ The TCM freezes the transmission adaptive functions.
^ The TCM requests the PCM to limit engine torque to 150 Nm (111 ft. lbs.).
^ The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Freeze Frame and Failure Records.
^ The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as Failure Record.
^ The TCM stores DTC P0736 in TCM history.

Conditions for Clearing the MIL/DTC
^ The PCM turns off the MIL after the third consecutive drive trip in which the TCM does not send a MIL illumination request.
^ A scan tool can clear the DTC.
^ The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
^ The TCM cancels the DTC default actions when the ignition is OFF long enough in order to power down the TCM.

Diagnostic Aids
Ask the customer about overloading the vehicle, exceeding the trailer towing limit, or towing in DRIVE (D).

Test Description

Step 1 - Step 9:

Step 10 - Step 17:

Step 18 - Step 20:

The numbers below refer to the step numbers on the diagnostic table.
5. This step determines that shift solenoid 4 or the U1 shift valve is stuck if the TCC applies in 2nd gear and stalls the engine.
6. This step determines if the OSS signal is skewed by a large factor.
7. This step determines if the ISS signal is skewed by a large factor.