Circuit Description
The DTC P1600 Control Module Long Term Memory Reset diagnostic detects a loss of battery voltage to the control module's keep alive memory circuit. 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 an intermittent condition. Refer to Intermittent Conditions .
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.
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The Diagnostic System Check-Engine Controls 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.
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This step checks whether a DTC P1600 is the result of a hard failure or an intermittent condition.
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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 | ||||
|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||||||
Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | ||||||
Does DTC P1600 set? | -- | Go to Step 3 | Go to Diagnostic Aids | |||||
Was a repair necessary? | -- | Go to Step 7 | Go to Step 4 | |||||
4 |
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 |
Is a DTC P1600 present? | -- | Go to Step 2 | Go to Step 8 | ||||
8 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |||||
