For 1990-2009 cars

### Circuit Description

The DTC P1500 Start Switch Circuit monitors the voltage signal that is sent from the ignition switch when starting the engine. When the engine is being cranked, the battery voltage is applied to the powertrain control module (PCM). The starter signal is mainly used to increase the fuel injection volume for the starting injection control. This signal passes through the transmission range (TR) switch. If this signal is not detected during engine cranking, the PCM will still allow the engine to start.

### Condition for Running the DTC

The engine was started and is running.

### Conditions for Setting the DTC

The engine is running but no starter signal was detected when the engine was cranking.

OR:

A high voltage is present at the PCM for at least 3 minutes after starting the engine.

### Action Taken When the DTC Sets

• | The PCM illuminates the malfunction indicator lamp (MIL) after 2 consecutive ignition cycles in which the diagnostic runs with the fault active.

• | The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer.

### 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

If the DTC P1500 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 P1500 diagnostic on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If DTC P1500 appears in the Not Ran Since Code Cleared list, the DTC P1500 diagnostic has not yet run. When DTC P1500 does not appear in the Not Ran Since Code Cleared list, the DTC P1500 diagnostic has run. If the MIL is NOT illuminated, and there is no Pending DTC Status in DTC Information, the DTC P1500 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 fault in the starter signal sensor circuit. Inspect the wiring harness and the components for an intermittent condition. Refer to Intermittent Conditions .

If DTC P1500 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining the vehicle operating conditions when the DTC was first set.

### 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 a fault is present.

3. This step checks for the correct voltage on the crank signal circuit. While the engine is cranking, the PCM crank signal terminal should have a voltage reading of 6-12 volts and after the engine is started, the PCM crank signal terminal should have a voltage reading of 0 volts.

4. Clearing the DTCs by removing the DOME fuse also clears the PCM long term memory. Using the scan tool to clear DTCs leaves the long term memory active. DTC emitting diagnostics may not run to completion as expected unless the long term memory is cleared. Removal of the DOME fuse also clears the time display of the radio. The DTC P1500 diagnostic can be monitored on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If a DTC P1500 appears in the Not Ran Since Code Cleared list, the DTC P1500 diagnostic has not yet run. When the DTC P1500 does not appear in the Not Ran Since Code Cleared list, the DTC P1500 diagnostic has run. If the MIL is NOT illuminated, and there is no Pending DTC Status in DTC Information, the DTC P1500 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.

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. Turn ON the ignition, leaving the engine OFF.
2. Perform the scan tool Clear DTC Information function.
3. Start the engine.
4. Run the engine for 3 minutes or more.
5. If the MIL is not illuminated, turn OFF the engine and repeat the action in the prior 2 steps.

Is a DTC P1500 set?

--

Go to Step 3

Go to Diagnostic Aids

3 |

1. Turn OFF the ignition.
2. Disconnect the PCM electrical connectors.
3. Turn ON the ignition, leaving the engine OFF.
4. Place the gear selector in PARK.
5. Measure the voltage of the start signal circuit with a DMM.
6. Crank the engine.
7. Measure the start signal circuit voltage with a DMM while cranking the engine.

Does the voltage equal the first specified value with the ignition ON, and within the second specified range while cranking the engine?

0 V

6-12 V

Go to Step 5

Go to Step 4

4 | Repair the open or the short in the crank signal circuit between the PCM and the transmission range (TR) switch. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 7 | --
5 |

1. Check for faulty electrical connections at the PCM.
2. Repair as necessary. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Was a repair necessary?

--

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. Turn OFF the ignition.
2. Remove the DOME fuse for 30 seconds.
3. Install the DOME fuse.
4. Reset the radio clock time. Refer to Radio/Audio System Description and Operation in Entertainment.
5. Start the engine.
6. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text or until the DTC P1500 diagnostic test has run.

Does the DTC run and pass?

--

Go to Step 8

Go to Step 2

8 | Use the scan tool in order to 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