For 1990-2009 cars

### 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 controller area network (CAN) DTCs U2104 or U0100.

• | The brake switch is released.

• | Trans. protection mode is OFF.

• | No TR switch DTC P0705.

• | No transmission fluid temperature (TFT) DTCs P0711, P0712, or P0713.

• | No ISS DTC P0717.

• | No OSS DTC P0722.

• | No engine speed DTC P0727.

• | No torque converter clutch (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 TCC is disabled.

• | The TCM freezes the transmission adaptive functions.

• | The TCM requests the PCM to limit engine torque to 150 N·m (111 lb ft).

• | 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

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

1. 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.

2. This step determines if the OSS signal is skewed by a large factor.

3. This step determines if the ISS signal is skewed by a large factor.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 | Inspect for correct transmission fluid level. Refer to Transmission Fluid Check . Is the transmission fluid level correct? | -- | Go to Step 4 | Go to Step 3
3 |

1. Visually inspect the transmission cooling system for fluid leaks. Refer to Fluid Leak Diagnosis .
2. Repair leaks as necessary.
3. Fill the transmission to the proper fluid level.

Did you find and correct the condition?

--

Go to Step 19

Go to Step 4

4 |

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

Important:

• | Before clearing the DTC, use the scan tool in order to record the PCM and the TCM Failure Records. Using the Clear Eng./Trans. DTC Info function erases the Failure Records from the PCM and TCM.

• | Using the Clear Eng./Trans. DTC Info function erases stored DTCs in both the powertrain control module (PCM) and the transmission control module (TCM).

3. Record the DTC Failure Records.
4. Clear the DTC.
5. Use the scan tool snapshot mode in order to record commanded gear and gear ratio.
6. Drive the vehicle in REVERSE (R) and record the gear ratio while accelerating.

Is the reverse gear ratio within the specified range?

2.54:1-3.81:1

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 5

5 | Drive the vehicle in 2nd gear. Does the engine stall when the transmission shifts into 2nd gear? | -- | Go to Step 10 | Go to Step 6
6 |

1. Drive the vehicle.
2. Observe Transmission OSS parameter with a scan tool.
3. Compare with a known good vehicle.

Is Transmission OSS parameter reading correctly?

--

Go to Step 7

Go to Step 15

7 |

1. Stop the vehicle and apply the parking brake.
2. Place the gear selector in PARK (P).
3. Allow the engine to idle.
4. Observe Transmission AT ISS parameter with a scan tool.

Is Transmission AT ISS parameter within the specified range?

400-800 RPM

Go to Step 8

Go to Step 14

8 | Perform a line pressure test. Refer to Line Pressure Check . Is the action complete? | -- | Go to Step 9 | --
9 |

1. Remove the control valve body cover (29).
2. Inspect the inside of the control valve body cover (29) for excessive sediment.

Did you find excessive amounts of sediment?

--

Go to Step 13

Go to Step 11

10 | Inspect the control valve body assembly (39) for the following conditions:

• | Stuck 3-4, 4-5 shift solenoid valve assembly (S4) - blue (303)

• | Stuck U1 shift valve (386)

Did you find any of the above conditions?

--

Go to Step 16

Go to Step 12

11 | Inspect the control valve body assembly (39) for the following conditions:

• | Stuck M1 shift valve (389)

• | Stuck U1 shift valve (386)

• | Stuck U2 shift valve (392)

• | Stuck neutral relay valve (356)

• | Stuck line pressure control solenoid valve assembly (SLT) (316)

Did you find any of the above conditions?

--

Go to Step 16

Go to Step 12

12 | Has the control valve body been serviced within the past 3 months or 4 828 km (3,000 mi)? | -- | Go to Step 13 | Go to Step 16
13 | Inspect the following items:

• | Direct clutch (C2) (556)

• | Low and reverse clutch (B3) (26)

• | 1-2, reverse clutch (B5) (620)

Is the action complete?

--

Go to Step 17

--

14 | Replace the input shaft speed sensor (73). Refer to Input Speed Sensor Replacement . Is the replacement complete? | -- | Go to Step 19 | --
15 | Replace the output shaft speed sensor (62). Refer to Output Speed Sensor Replacement . Is the replacement complete? | -- | Go to Step 19 | --
16 | Repair or replace the control valve body assembly (39). Refer to Control Valve Body Cover Replacement . Is the action complete? | -- | Go to Step 18 | --
17 | Repair or replace the transmission. Refer to Transmission Replacement . Is the action complete? | -- | Go to Step 18 | --
18 |

1. Replace the transmission fluid. Refer to Transmission Fluid Replacement .
2. Inspect for the correct level of transmission fluid.
3. Add new fluid as necessary.

Important: The Reset Trans Adapts function will clear all adapt cells. This may affect transmission performance. The TCM will update the adapt cell values as the vehicle is driven.

4. Use the scan tool in order to perform the following:

• | Reset oil life monitor to 100 percent.

• | Reset Trans Adapts.

Did you complete the above procedures?

--

Go to Step 19

--

19 | Perform the following procedure in order to verify the repair:

1. Select DTC.
2. Select Clear Info.
3. Operate the vehicle.
4. Select Specific DTC.
5. Enter DTC P0736.

Does the DTC reset?

--

Go to Step 2

Go to Step 20

20 | 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