For 1990-2009 cars

### Circuit Description

The body control module (BCM) contains the 2-amp EPS fuse. This fuse and the ignition 1 voltage circuit supply ignition voltage to the power steering control module (PSCM). This ignition voltage is used to wake up the PSCM. The PSCM receives a class 2 power moding message from the BCM to determine the position of the ignition switch. When a power mode message is received, the PSCM monitors the ignition 1 voltage circuit to detect if a short to voltage, short to ground, or an open exists.

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC C0845 Device Ignition 1 Circuit

This vehicle has DTCs which include DTC Symptoms. For more information on DTC Symptoms, refer to DTC Symptom Description .

DTC Symptom | DTC Symptom Descriptor
--- | ---
01 | Short to Battery +
06 | Short to Ground or Open

### Conditions for Running the DTC

The PSCM has 9-16 volts.

### Conditions for Setting the DTC

• | The class 2 power mode message indicates OFF, and the ignition 1 voltage circuit is shorted to voltage.

• | The class 2 power mode message indicates ON, and the ignition 1 voltage circuit is shorted to ground or open.

• | DTCs U1300 and U1301 are not set.

### Action Taken When the DTC Sets

• | DTC C0847 is stored in memory.

• | The instrument panel cluster (IPC) message center displays the PWR STR warning message.

• | The EPS system is disabled.

### Conditions for Clearing the DTC

• | A current DTC will clear when the malfunction is no longer present.

• | A history DTC will clear after 100 consecutive malfunction-free ignition cycles.

• | Using a scan tool

### Diagnostic Aids

The ignition 1 voltage circuit supplies several other control modules with ignition voltage. Before preceding with the diagnostic table below, ensure no other control modules that use the ignition 1 circuit for their ignition voltage supply have any ignition voltage malfunctions present, such as the sensing and diagnostic module (SDM) or the cruise control module (CCM). Refer to Power Distribution Schematics . If an intermittent malfunction exists, refer to Testing for Intermittent Conditions and Poor Connections for further diagnosis.

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. This step tests if the malfunction is intermittent.

2. This step tests if a short to ground exists in the ignition 1 voltage circuit, or in the PSCM.

Step | Action | Yes | No
--- | --- | --- | ---
Connector End Views Reference: Power Steering Connector End Views
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 |

1. Install a scan tool.
2. Turn ON the ignition, with the engine OFF.
3. With a scan tool, attempt to establish communication with the power steering control module (PSCM).

Does the scan tool communicate with the PSCM?

Go to Step 6

Go to Step 3

3 |

1. Turn OFF the ignition.
2. Inspect the 2 A EPS fuse for an open.

Is the fuse open?

Go to Step 4

Go to Step 7

4 |

1. Replace the 2 A EPS fuse.
2. Turn ON the ignition, with the engine OFF.

Does the fuse open?

Go to Step 5

Go to Diagnostic Aids

5 | Test the ignition 1 voltage circuit of the PSCM for a short to ground. Refer to Testing for Short to Ground and Wiring Repairs . Did you find and correct the condition? | Go to Step 11 | Go to Step 10
6 | Test the ignition 1 voltage circuit for a short to voltage. Refer to Testing for a Short to Voltage and Wiring Repairs . Did you find and correct the condition? | Go to Step 11 | Go to Diagnostic Aids
7 | Test the ignition 1 voltage circuit of the PSCM for an open. Refer to Circuit Testing and to Wiring Repairs . Did you find and correct the condition? | Go to Step 11 | Go to Step 8
8 | Inspect for poor connections at the harness connector of the body control module (BCM). Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs . Did you find and correct the condition? | Go to Step 11 | Go to Step 9
9 | Inspect for poor connections at the harness connector of the PSCM. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs . Did you find and correct the condition? | Go to Step 11 | Go to Step 10
10 | Replace the electronic power steering (EPS) assembly. Refer to Steering Column Replacement . Did you complete the replacement? | Go to Step 11 | --
11 |

1. Use the scan tool in order to clear the DTCs.
2. Operate the vehicle within the Conditions for Running the DTC.

Does DTC C0845 reset?

Go to Step 2

System OK