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For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2006 🢒 GMC Sierra Denali 🢒 Transmission/Transaxle 🢒 Automatic Transmission - Allison 🢒 DTC P0736

Circuit Description

The transmission control module (TCM) uses input from the input speed sensor (ISS) and output speed sensor (OSS) to determine gear ratios. The TCM then compares the known gear ratio to the calculated gear ratio for the current gear.

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
    • DTCs P0716, P0717, P0721, P0722, P0875, and P0876 are not active.
    • The components are powered and ignition voltage is greater than 9.0 volts and less than 18 volts.
    • Output speed exceeds 200 RPM.
    • REVERSE is selected and attained.

Conditions for Setting the DTC

DTC P0736 sets when the calculated REVERSE range ratio, steady state, detected by the TCM differs from the known REVERSE range ratio.

Action Taken When the DTC Sets
    • The TCM illuminates the malfunction indicator lamp (MIL).
    • The transmission will lock in NEUTRAL.
    • DTC P0736 is stored in TCM history.
    • The TCM freezes shift adapts.
    • The TCM inhibits torque converter clutch (TCC) engagement.

Conditions for Clearing the DTC

A scan tool can clear the code from TCM history. The TCM automatically clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without failure.

Diagnostic Aids
    • Incorrect ratio codes typically indicate mechanical conditions with specific clutches, such as 3-5-Reverse clutch and low and reverse clutch for REVERSE range.
    •  Incorrect ratio code could indicate a hydraulically failed solenoid. Observe DTC information for specific solenoid.
    • Clutch test mode can be used to measure stall speed. Observe turbine speed signal. If the turbine speed signal does not return to zero or rises during the stall test, a leak or obstruction in a specific clutch apply circuit could be present.
    •  You may have to drive the vehicle in order to experience a condition.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step tests ignition voltage.

    2.

  2. This step tests speed sensor readings.

    3.

  3. This step tests for turbine speed not remaining at zero in REVERSE range.

Step

Action

Value

Yes

No

Schematic Reference: Automatic Transmission Controls Schematics

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

Measure the transmission fluid level. Refer to Transmission Fluid Check .

Is the transmission fluid level correct?

--

Go to Step 3

Go to Transmission Fluid Check

3

  1. Install the scan tool.
  2. Turn ON the ignition, with the engine OFF.

    3. Important: Before clearing the DTC, use the scan tool in order to record the Freeze Frame and Failure Records for reference. The Clear Info function will erase the data.

  3. Record the DTC Freeze Frame and Failure Records.
  4. Clear the DTC.
  5. Using the scan tool, measure ignition voltage.

Is the voltage within the specified range?

9-18 V

Go to Step 4

Go to DTC P0562 for low voltage or DTC P0563 for high voltage

4

  1. Start the engine.
  2. Select REVERSE range.
  3. Using the scan tool, observe the gear ratio.

Is the correct REVERSE range ratio shown?

-4.49:1

Go to Step 5

Go to Diagnostic Aids

5

  1. Turn the ignition ON.
  2. Start the engine and run at idle.
  3. Using the scan tool, monitor engine, turbine, and output speed readings in REVERSE range with the vehicle brakes applied.

Is speed sensor data erratic?

--

Go to the appropriate speed sensor DTC

Go to Step 6

6

    Notice: Do not perform a full RPM stall test in reverse range, or vehicle damage may occur.

  1. Apply vehicle brakes and select REVERSE.
  2. With the engine at idle and REVERSE range attained, turbine speed should go to zero.
  3. Using the scan tool, monitor turbine speed while increasing engine speed to 1,000 RPM.

Did turbine speed remain at zero?

--

Go to Diagnostic Aids

Go to Step 7

7

  1. Remove the transmission oil pan. Refer to Automatic Transmission Fluid and Filter Replacement .
  2. Inspect for contaminated fluid and excessive material in the pan.

Is the fluid contaminated or excessive material found in the pan?

--

Go to Step 8

Go to Step 9

8

Remove the transmission for overhaul or replacement. Refer to Transmission Replacement .

Did you complete the replacement?

--

Go to Step 11

--

9

Inspect for a stuck or sticking pressure control valve. Refer to Control Valve Body Cleaning and Inspection .

Did you find and correct a condition?

--

Go to Step 11

Go to Step 10

10

Replace pressure control solenoid 2 (PCS2). Refer to Control Valve Solenoid Replacement .

Did you complete the replacement?

--

Go to Step 11

--

11

Perform the following procedure in order to verify the repair:

  1. Clear the DTC.
  2. Start the engine.
  3. Using the scan tool, monitor REVERSE gear ratio and operate the vehicle under normal operating conditions.
  4. Select Specific DTC.
  5. Enter DTC P0736.

Has test run and passed?

--

Go to Step 12

Go to Step 2

12

With the scan tool, observe the stored information, capture info and DTC info.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle

System OK