For 1990-2009 cars
Engine Controls Components
Cell 23: Power, Ground, MIL, and DLC
OBD II Symbol Description Notice
Powertrain Control Module Connector End Views
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

A Class 2 serial data communications system is used on this vehicle in order to allow various modules to communicate and share information with each other. Each bit of information has one of two lengths: long or short. This allows for the reduction of the vehicle wiring, and for the transmission and reception of multiple signals over a single wire. The messages carried on the Class 2 serial data stream are also prioritized. If two messages attempt to establish communications on the data line at the same time, the message with the higher priority will continue. The message with the lower priority message will wait.

All modules on the Class2 serial data line send out a periodic identifier message. The PCM is listening for the identifier messages from the EBCM and the BCM as well as an echo of the PCM identifier message. If a module cannot respond to the PCM, a DTC is stored.

### Conditions for Setting the DTC

The PCM has lost communication with the Body Control Module (BCM) after the PCM received a Theft Passed message from the BCM.

### Action Taken When the DTC Sets

• | The PCM will record operating conditions at the time the diagnostic fails. This information will store in the Freeze Frame and Failure Records buffers.

• | A history DTC stores.

### Conditions for Clearing the MIL/DTC

• | A history DTC will clear after 40 consecutive warm up cycles without a fault.

• | A scan tool can clear the DTCs.

### Diagnostic Aids

Attempting to start the vehicle by bypassing the Passlock ll system or by substituting parts without performing the password learn procedure may set a DTC P1631 and a P1632.

If no password is received, a DTC U1064 and P1632 may be set.

An intermittent may be caused by the following conditions:

• | Poor electrical terminal connection

• | Broken wire inside the insulation

Thoroughly check any suspected circuitry for the following items:

• | Backed out terminals or improper mating

• | Improperly formed or damaged terminals

• | Poor terminal to wiring connections

• | Physical damage to the wiring harness

• | Corrosion

### Test Description

Numbers below refer to the step numbers on the Diagnostic Table.

1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored in the scan tool for later reference.

2. If the serial data circuit to the Body Control Module (BCM) was not open, then the serial communication loss to the PCM lies within the BCM.

3. The replacement PCM must be reprogrammed and the crankshaft position system variation procedure must be performed. Refer to the latest Techline procedures for PCM reprogramming and the Crankshaft Position Variation Procedure.

4. If the serial data loss occurred after a good theft password has been received, the PCM will allow the vehicle to be started on following attempts. After making the necessary repairs to the vehicle the PCM must be reprogrammed and the password learn procedure and the crankshaft position system variation procedures must be completed to allow the theft system to operate properly.

5. If no malfunctions have been found at this point and no additional DTCs were set, refer to Diagnostic Aids for additional checks and information.

#### DTC P1626 - No Password Received from Body Control Module (BCM)

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 |

1. Turn ON the ignition switch leaving the engine OFF.
2. Install a scan tool.
3. Check if DTC P1626 is Current or History with the scan tool.

Was DTC P1626 Current?

--

Go to Step 3

Go to Step 13

3 |

1. Crank the engine.
2. Check if DTC P1626 is still Current with the scan tool.

Is DTC P1626 still Current?

--

Go to Step 4

Go to Step 13

4 | Check if DTC U1064 is set with the scan tool. Is DTC U 1064 also set? | -- | Go to Step 5 | Go to Step 7
5 | Check if DTC U1064 is Current or in History with the scan tool. Is DTC U1064 Current? | -- | Go to DTC U1064 Loss of BCM and/or VTD Communication | Go to Step 6
6 |

1. Turn OFF the ignition switch.
2. Turn ON the ignition switch leaving the engine OFF.
3. Crank the engine.
4. Wait for at least 5 seconds to verify that DTC U1064 does not become Current.
5. Check if DTC U1064 is Current or History with the scan tool.

Is DTC U1064 Current?

--

Go to DTC U1064 Loss of BCM and/or VTD Communication

Go to Step 7

7 | Attempt to communicate with the Body Control Module (BCM) with the scan tool. Can you communicate with the BCM? | -- | Go to Step 8 | Go to Step 10
8 | Check for any Body Control Module (BCM) DTCs with the scan tool. Are there any BCM DTCs set? | -- | Go to Body Control Module System Check | Go to Step 9
9 | Does the Body Control Module (BCM) indicate the password is valid? | -- | Go to Step 15 | Go to Step 11
10 | Attempt to communicate to Electronic Brake Control Module (EBCM) and the IPC with the scan tool. Can you communicate to the Electronic Brake Control Module (EBCM) and IPC with the scan tool? | -- | Go to Step 11 | Go to Data Link Connector Diagnosis
11 |

1. Disconnect the Body Control Module (BCM) electrical connector.
2. Disconnect the PCM electrical connector.
3. Check the serial data circuit between the control modules for the following conditions:

• | Open circuit

• | Poor electrical terminal connection(s)

4. Repair the condition(s) as necessary. Refer to Wiring Repairs .

Was a repair necessary?

--

Go to Step 12

Go to Body Control Module System Check

12 | Attempt to communicate to the BCM with the scan tool. Can you communicate with the BCM with the scan tool? | -- | Go to Step 14 | Go to Body Control Module System Check
13 |

1. Check the electrical terminal connection(s) at the PCM and the BCM for the following condition(s):

• | Poor electrical terminal connection(s)

• | Electrical terminal tension

2. Repair the condition(s) as necessary. Refer to Wiring Repairs .

Was a repair necessary?

--

Go to Step 14

Go to Body Control Module System Check

14 | Perform the Password Learn Procedure. Refer to Password Learn . Is the action complete? | -- | Go to Step 16 | --
15 |

1. Turn OFF the ignition switch.
2. Replace the PCM. Refer to the Powertrain Control Module Replacement/Programming .

Is the action complete?

--

Go to Step 16

--

16 |

1. The PCM may need to be reprogrammed and the Password Learn Procedure performed. Refer to the following procedures:

• | Powertrain Control Module Replacement/Programming

• | Crankshaft Position System Variation Learn

• | Password Learn

2. Using the scan tool, clear DTCs.
3. Start engine.
4. Idle the engine at normal operating temperature.
5. Operate the vehicle within the conditions for setting this DTC as specified in the supporting text.

Does the scan tool indicate that this diagnostic ran and passed?

--

Go to Step 17

Go to Step 2

17 | Check if any additional DTCs are set. Are any DTCs displayed that have not been diagnosed? | -- | Go to the applicable DTC table | System OK