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. If DTC P1600 is set, the PCM will not store any other DTCs.
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 after the third consecutive trip which the diagnostic runs without a fault. |
| • | The PCM clears a history DTC after 40 consecutive warm-up cycles without a fault. |
| • | Clear the DTCs using the scan tool Clear DTC Information function. |
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 block-underhood. If the EFI fuse was faulty, or if there was no power 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 Intermittent Conditions | |
Does the DMM indicate the specified value? | B+ | Go to Step 5 | Go to Step 4 | |
4 | Repair the open in the battery positive voltage circuit between the PCM and the fuse block-underhood. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 6 | -- |
5 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 6 | -- |
6 |
Is a DTC P1600 present? | -- | Go to Step 2 | Go to Step 7 |
7 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
