For 1990-2009 cars

Refer to Engine Controls Schematic

#### Power and Ground

Engine Controls Components
MIL and DLC
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Cell 14: G105 and G106 (1 of 2)
Cell 14: SP254 and SP261
Cell 10: Ignition Switch, IGN Fuse, and ST Fuse
Cell 10: Ignition Switch, IGN Fuse, and ST Fuse
Cell 10: Alt-S, AM2, Dome, EFI, Hazard, Horn, and Main Fuses
.

### 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 the PCM keep alive memory and the air-fuel ratio adaptive control memory.

### Conditions for Setting the DTC

No battery voltage at the PCM battery positive voltage circuit.

### Action Taken When the DTC Sets

• | The PCM illuminates the malfunction indicator lamp (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:

• | Any backed-out terminals

• | Any improper mating of terminals

• | Any broken electrical connector locks

• | Any improperly formed or damaged terminals

• | Any faulty terminal-to-wire connections

• | Any physical damage to the wiring harness

• | A broken wire inside the insulation

• | Any corrosion of the electrical connections, the splices, or the terminals

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

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 electrical connector of fuse and relay block 1 . 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 | Values | 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 DTC P1600 set?

--

Go to Step 3

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 C3 harness cavity 1 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 conditions that set the DTC.
2. Start the engine.
3. Run the engine to obtain normal operating temperature.
4. Review the scan tool data and check for DTCs. If no DTCs are stored the repair is complete.

Are any DTCs displayed on the scan tool?

--

Go to Diagnostic Trouble Code (DTC) List

System OK