For 1990-2009 cars
Engine Controls Components
Cell 20: Main Power Feed
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

Battery positive voltage is supplied to the powertrain control module (PCM) even when the ignition switch is OFF. The battery positive voltage is used for PCM keep alive memory and the air-fuel ratio adaptive control memory.

### Conditions for Setting the DTC

No batttery voltage at the PCM Battery Positive Voltage circuit.

### Action Taken When the DTC Sets

• | The PCM illuminates the MIL.

• | The PCM stores the conditions that were present when the DTC set as Freeze Frame data.

### Conditions for Clearing the MIL/DTC

• | The PCM turns the MIL OFF on the third consecutive trip cycle during which the diagnostic has run and the fault condition is no longer present.

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

• | A DTC can be cleared by using the scan tool Clear Information function.

### Diagnostic Aids

If DTC P1600 is set, the PCM will not store any other DTCs.

An intermittent malfunction may be caused by a fault in the battery positive voltage electrical circuit. Inspect the wiring harness and components for any of the following conditions:

• | Backed out terminals.

• | Improper mating of terminals.

• | Broken electrical connectors locks.

• | Improperly formed or damaged terminals

• | Faulty terminal to wire connections.

• | Physical damage to the wiring harness.

• | A broken wire inside the insulation.

• | Corrosion of electrical connections, splices, or terminals.

Repair any electrical circuit faults that were found. Refer to Wiring Repairs .

The information included in the Freeze Frame data can be useful in determining the vehicle operating conditions when the DTC first set.

### Test Description

The numbers below refer to the step numbers in the Diagnostic Table.

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

2. This step checks whether a DTC P1600 is the result of a hard failure or an intermittent condition.

3. This step checks for battery positive voltage at the Fuse and Relay Block 1 electrical connector. If the EFI fuse was faulty, or if there was no voltage to the fuse, the vehicle would not start and there would be no MIL or serial data communication.

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

1. Perform the scan tool Clear DTC Information function.
2. Start the engine.
3. Run the engine to obtain normal operating temperature.

Does a DTC P1600 set?

--

Go to Step 3

Fault not Present-Go to Diagnostic Aids

3 |

1. Check for any of the following conditions:

• | A faulty electrical connection at terminal C2-8 of the Fuse and Relay Block 1.

• | No battery positive voltage from the EFI fuse at terminal C2-8 of the Fuse and Relay Block 1.

2. Repair as necessary.

Was a repair necessary?

--

Go to Step 7

Go to Step 4

4 |

1. Disconnect the PCM electrical connector C3.
2. Measure the voltage of the battery positive voltage circuit at PCM connector harness cavity C3-1, RED/WHT wire, with a DMM.

Does the DMM indicate the specified value?

B+

Go to Step 6

Go to Step 5

5 | Repair the open in the battery positive voltage circuit between the PCM and the Fuse and Relay Block 1. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 7 | --
6 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | Go to Step 7 | --
7 |

1. Perform the scan tool Clear DTC Information function and road test the vehicle within the Freeze Frame conditins that set the DTC.
2. Start the engine.
3. Run the engine to obtain normal operating temperatur
4. Review the scan tool data and check for DTCs. If no DTCs are stored the repair is complete.

Are any DTCs displayed on scan tool?

--

Go to the applicable DTC table

System OK