For 1990-2009 cars

### Circuit Description

Modules that are connected to the shared communication circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. The modules have pre-recorded information about what messages are needed to be exchanged on the serial data circuits for each virtual network. The messages are usually supervised and some periodic messages are used by the receiver module as an availability indication of the transmitter module. Each message contains the identification number of the transmitter module.

### DTC Descriptors

This diagnostic procedure supports the following DTCs:

• | DTC U0100 Lost Communication with ECM/ transmission control module (TCM)

• | DTC U0140 Lost Communication with body control (IPC) system

• | DTC U0167 Theft Deterrent Fuel Enable Signal Not Received

### Conditions for Running the DTC

The ignition voltage is between 9.0 volts and 19.0 volts.

### Conditions for Setting the DTC

#### U0100

No valid ECM CAN message for 12 seconds.

#### U0140

No valid IPC CAN message for 12 seconds.

#### U0167

No valid immobilizer message for 1.26 seconds.

### Actions Taken When DTC Sets

• | DTCs U0100 and U0167 are Type A DTCs.

• | DTC U0140 is a Type C DTC.

### Conditions for Clearing the MIL/DTC

• | DTCs U0100 and U0167 are Type A DTCs.

• | DTC U0140 is a Type C DTC.

Step | Action | Yes | No
--- | --- | --- | ---
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 | Test the following circuits of the module that is not communicating for an open or a short to ground:

• | The battery positive voltage input circuits

• | The battery positive voltage output circuits

• | The ignition voltage input circuits

• | The ignition voltage output circuits

• | The switched battery positive voltage circuits

Did you find and correct the condition?

Go to Step 7

Go to Step 3

3 |

1. Turn OFF the ignition.
2. Test the ground circuits of the module that is not communicating for an open.

Did you find and correct the condition?

Go to Step 7

Go to Step 4

4 | Test the CAN serial data circuits of the module that is not communicating for an open. Did you find and correct the condition? | Go to Step 7 | Go to Step 5
5 | Inspect the harness connectors of the module that is not communicating for poor connections and terminal tension at the following circuits:

• | The battery positive voltage input circuits

• | The battery positive voltage output circuits

• | The ignition voltage input circuits

• | The ignition voltage output circuits

• | The switched battery positive voltage circuits

• | The ground circuits

• | The CAN serial data circuits

Did you find and correct the condition?

Go to Step 7

Go to Step 6

6 | Replace the module that is not communicating. Did you complete the replacement? | Go to Step 7 | --
7 |

1. Clear the DTCs with a scan tool.
2. Turn the ignition OFF for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Setting the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

Go to Step 2

Go to Step 8

8 | Check if any additional DTCs are set. Are there any DTCs that have not been diagnosed? | Go to Diagnostic Trouble Code (DTC) List - Vehicle | System OK