For 1990-2009 cars

### Circuit Description

This DTC indicates that the ECM has been programmed with a frequency code that does not match the code in the theft deterrent module.

### Conditions for Running the DTC

Engine cranking

### Conditions for Setting the DTC

The ECM has been programmed with a frequency code that does not match the code in the theft deterrent module.

### Action Taken When the DTC Sets

The ECM will not illuminate the malfunction indicator lamp (MIL).

### Conditions for Clearing the MIL/DTC

• | The DTC clears after forty consecutive warm-up cycles if no failures report by this diagnostic or any other non-emission related diagnostic.

• | The scan tool clears the MIL/DTC.

### Diagnostic Aids

• | The wrong ignition key, or the use of a key without a transponder will cause this DTC to set as well as a no-start.

• | If the ECM and the theft deterrent module have not been properly programmed, this DTC may set and the vehicle will not start. Refer to Theft Deterrent System in Engine Accessories for the programming instructions.

#### DTC P1503 - Theft Deterrent System - Password Incorrect

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

1. Attempt to reprogram the engine control module (ECM) with the correct frequency code.
2. Attempt to start the vehicle.

Does DTC P01503 reset?

--

Go to Diagnostic Aids

Go to Step 3

3 |

1. Using the scan tool, clear the DTCs.
2. Start the engine.
3. Allow the engine to idle until the engine reaches the normal operating temperature.
4. Select DTC and the Specific DTC function.
5. Enter the DTC number that was set.
6. Operate the vehicle within the Conditions for Running this DTC until the scan tool indicates that the diagnostic Ran.

Does the scan tool indicate that the diagnostic Passed?

--

Go to Step 4

Go to Step 2

4 | Does the scan tool display any additional, undiagnosed DTCs? | -- | Go to the applicable DTC table | System OK