For 1990-2009 cars

### Circuit Description

The DTC P1510 Control Module Long Term Memory Reset diagnostic monitors the battery voltage supply to the PCM. The battery voltage is supplied to the powertrain control module (PCM) for the retention of certain long term memory data. Diagnostic trouble codes (DTCs) and learned engine control parameters are kept in the PCM memory even when the ignition is OFF. A DTC P1510 sets and the PCM long term memory information is lost when the voltage to the memory power circuit is interrupted.

### Condition for Running the DTC

The engine is running.

### Conditions for Setting the DTC

• | No back-up power is supplied to the PCM after starting the engine.

• | The condition is present for 5 seconds.

### Action Taken When the DTC Sets

• | The PCM illuminates the malfunction indicator lamp (MIL).

• | The PCM stores DTC P1510 as long as the ignition is not turned OFF.

### Conditions for Clearing the MIL/DTC

• | The MIL turns OFF after 3 consecutively passing trips without a fault present.

• | A history DTC clears after 40 consecutive warm-up cycles without a fault.

• | Perform the scan tool Clear DTC Information function.

### Diagnostic Aids

The PCM will indicate a DTC P1510 as long as the ignition is ON. As soon as the ignition is turned Off the PCM will lose memory of DTC P1510 and DTC P1510 will not be stored.

Check for an open fuse. Replace any open fuses and retest.

If the DTC P1510 is intermittent, driving the vehicle under the following conditions can verify whether the fault is present. Perform the scan tool Clear DTC Information function. Road test the vehicle while monitoring the DTC P1510 diagnostic on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If DTC P1510 appears in the Not Ran Since Code Cleared list, the DTC P1510 diagnostic has not yet run. When DTC P1510 does not appear in the Not Ran Since Code Cleared list, the DTC P1510 diagnostic has run. If the MIL is NOT illuminated and there is no Pending DTC Status in DTC Information, the DTC P1510 diagnostic has passed. The DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. DO NOT forget that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for Current or Pending status in order to determine the outcome of the diagnostic test involved.

An intermittent malfunction may be caused by a problem in the memory power input circuit. Inspect the wiring harness and components for an intermittent condition. Refer to Intermittent Conditions .

### Test Description

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

1. 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.

2. This step determines if the fault is present.

3. This step checks for voltage at the PCM when the ignition is OFF. The PCM should indicate battery voltage on this terminal under all operating conditions.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Engine Controls Schematics
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | Go to Diagnostic System Check - Engine Controls
2 |

1. Start the engine.
2. Perform the scan tool clear DTC information function.
3. Run the engine for at least 1 minute or until the MIL illuminates.
4. Turn OFF the ignition.

Is a DTC P1510 set?

--

Go to Step 3

Go to Diagnostic Aids

3 |

1. Turn OFF the ignition.
2. Backprobe the battery positive voltage circuit at the PCM with a DMM connected to ground.

Is the voltage near the specified value?

B+

Go to Step 5

Go to Step 4

4 | Repair the open or the short in the battery positive voltage circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 7 | --
5 |

1. Inspect for a poor connection at the PCM. Repair as necessary. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
2. Repair the condition as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and repair the condition?

--

Go to Step 7

Go to Step 6

6 | Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 7 | --
7 |

1. Use the scan tool in order to clear the DTCs.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Run the engine for 1 minute.

Is a DTC P1510 set?

--

Go to Step 8

Go to Step 2

8 | With the scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List | System OK