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.
This diagnostic procedure supports the following DTC:
DTC P0736 Incorrect Reverse Ratio
• | 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. |
The TCM commands reverse and the actual gear ratio is not within 2.54:1-3.81:1 for 6 seconds:
• | 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. |
• | 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. |
Ask the customer about overloading the vehicle, exceeding the trailer towing limit, or towing in DRIVE (D).
The numbers below refer to the step numbers on the diagnostic table.
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.
This step determines if the OSS signal is skewed by a large factor.
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 | |||||||||||
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 |
Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 4 | ||||||||||
4 |
Important:
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 | ||||||||||
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 | |||||||||||
Is Transmission OSS parameter reading correctly? | -- | Go to Step 7 | Go to Step 15 | |||||||||||
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 |
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:
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:
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:
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 |
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.
Did you complete the above procedures? | -- | Go to Step 19 | -- | ||||||||||
19 | Perform the following procedure in order to verify the repair:
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? | -- | System OK |