For 1990-2009 cars

## DTC P0727 3.0L (L81)

### Circuit Description

Engine speed information is sent to the transmission control module (TCM) by the engine control module (ECM) through the controller area network (CAN). A two-wire circuit is used to communicate data between the ECM and TCM, CAN H and CAN L. A fault in the CAN will not cause DTC P0727 to set by itself. If a communication fault occurs, other DTCs will set before P0727.

When the ECM sends the TCM an invalid engine speed, DTC P0727 sets. DTC P0727 is a type A DTC.

### Conditions for Running the DTC

• | No HSCAN DTCs U2103, or U2105.

• | The ignition voltage is 8-18 volts.

### Conditions for Setting the DTC

The engine speed is invalid for 2.0 seconds.

### Action Taken When the DTC Sets

• | The TCM requests the ECM to illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met.

• | The TCM commands maximum line pressure.

• | The TCM calculates a default engine speed based on transmission input shaft speed.

• | The TCM freezes transmission adaptive functions.

• | The ECM records the operating conditions when the Conditions for Setting the DTC are met. The ECM 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 Records.

• | The TCM stores DTC P0727 in TCM history.

### Conditions for Clearing the MIL/DTC

• | The ECM 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 MIL/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 switch is OFF long enough in order to power down the TCM.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Diagnostic System Check - Engine Controls? | -- | Go to Step 2 | Go to Diagnostic System Check - Engine Controls in Engine Controls - 3.0L (L81)
2 |

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

Important:

• | Before clearing the DTC, use the scan tool in order to record the Freeze Frame and Failure Records. Using the Clear Info function erases the Freeze Frame and Failure Records from both the ECM and the TCM.

• | Record the DTC Freeze Frame and Failure Records.

3. Record the DTC Failure Records.

Did you record any ECM Failure Records?

--

Go to Diagnostic Trouble Code (DTC) List in Engine Controls - 3.0L (L81)

Go to Step 3

3 | Did you record a TCM Failure Record for DTC U2105? | -- | Go to DTC U2105 in Data Link Communications | Go to Step 4
4 |

1. Clear the DTC.
2. Turn the ignition OFF for at least 30 seconds.
3. Start and idle the engine.
4. Observe the Engine Speed on the scan tool.

Is the Engine Speed within the specified range?

500-1,000 RPM

Go to Step 5

Go to Step 6

5 | Road test the vehicle using various engine speeds. Did DTC P0727 reset? | -- | Go to Step 7 | Go to Intermittent Conditions in Engine Controls - 3.0L (L81)
6 |

1. Select Engine Data on the scan tool.
2. Observe the scan tool Engine Speed parameter.

Is the Engine Speed value within the specified range?

500-1,000 RPM

Go to Step 7

Go to Step 8

7 | Did any other DTCs set? | -- | Go to Diagnostic Trouble Code (DTC) List in Engine Controls - 3.0L (L81) | Go to Step 8
8 | Replace the ECM. Refer to Engine Control Module Replacement in Engine Controls - 3.0L (L81). Is the action complete? | -- | Go to Step 9 | --
9 | Perform the following procedure to verify the repair:

1. Select DTC on the scan tool.
2. Select Clear Info.
3. Start the engine.
4. Operate the engine at varying speeds.
5. Select Specific DTC.
6. Enter DTC P0727.

Has the test run and passed?

--

Go to Step 10

Go to Step 2

10 | 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 in Engine Controls - 3.0L (L81) | System OK