Refer to
Power, Ground, CPP, AT, and Cruise Control Brake Switch
in Engine Controls
Schematics.
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.
All modules on the Class 2 serial data line send out a periodic identifier message.
If the PCM does not receive an identifier message from a module, the PCM assumes that there is a loss of communication and a DTC is stored. A DTC P1626 will set after the engine has been started and there is a lost of communication between the PCM and the body control module (BCM). Since DTC P1626 is set after the engine has been started, the theft protection is bypassed at key-on. The vehicle will start, but as long as DTC P1626 is set there is no theft protection.
Conditions for Running the DTC
| • | The ignition is ON. |
| • | The system voltage is between 11 and 16 volts. |
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. |
| • | Use 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 inspect 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
The number below refers to the step number on the diagnostic table.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | |
2 | Use a scan tool in order to determine if DTC U1064 is also set. Is DTC U1064 also set? | -- | Go to DTC U1001-U1254 Loss of XXX Communications in Data Communications | Go to Step 3 |
3 | Use a scan tool in order to determine if any body control module (BCM) DTCs are set. Are there any BCM DTCs set? | -- | Go to Diagnostic System Check - Body Control System in Body Control System | Go to Step 4 |
4 | Use a scan tool in order to determine if the BCM password is valid. Is the password valid? | -- | Go to Step 5 | Go to Diagnostic System Check - Body Control System in Body Control System |
5 | Perform the Password Learn Procedure. Refer to Password Learn . Did you complete the Password Learn Procedure? | -- | Go to Step 8 | Go to Step 6 |
6 |
Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 7 |
|
Important:: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the repair? | -- | Go to Step 8 | -- | |
8 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
