For 1990-2009 cars

Schematic Reference: Engine Controls Schematics

### Circuit Description

The distributor ignition system supplies two timing inputs to the PCM, a high resolution signal (180 pulses per one crankshaft revolution) and a low resolution signal (4 pulses per one crankshaft revolution). The PCM can determine if one of the timing inputs is not being received by comparing the two inputs. If the PCM detects the high resolution timing pulse without detecting the low resolution timing pulse, DTC P1371 will set.

The high and low resolution circuits toggle between 0 and 5 volts as the camshaft turns. The following malfunctions to the low resolution circuit will cause a DTC P1371 to set:

• | An open.

• | A short to voltage.

• | A short to ground.

• | A defective ignition module within the distributor.

### Conditions for Setting the DTC

• | The PCM detects a predetermined amount of high resolution pulses before detecting any low resolution pulses.

### Action Taken When the DTC Sets

• | The PCM will illuminate the Malfunction Indicator Lamp (MIL) when the diagnostic runs and fails.

• | The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and/or Failure Records.

• | The injector will be disabled for the entire ignition cycle.

### Conditions for Clearing the MIL/DTC

• | The PCM will turn the MIL OFF after three consecutive drive trips that the diagnostic runs and does not fail.

• | A last test failed (Current DTC) will clear when the diagnostic runs and does not fail.

• | A History DTC will clear after forty consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

• | PCM battery voltage is interrupted.

• | Using a Scan tool.

### Diagnostic Aids

• | For any test that requires probing the PCM or a component harness connector, must use the Connector Test Adapter Kit J 35616-A. Using this kit will prevent damage to the harness connector terminals.

• | DTC P1371 will set if the high and low resolution circuits are shorted together. Before replacing any components, inspect the low and high resolution circuits for being shorted.

• | When an intermittent DTC P1371 occurs, a misfire will be apparent. To locate an intermittent, use the scan tools snapshot feature. Try to duplicate the conditions under which the misfire is present. When reviewing captured data, watch for any abnormal high and low resolution timing pulses.

• | If DTC P1351 and/or DTC P1361 is also set with a DTC P1371, and no external fault can be found, replace the PCM. If only DTC P1371 is set and the distributor connections are OK, replace the distributor.

• | If distributor components must be replaced, check distributor vent system operation. Refer to Distributor Ignition System.

• | If a DTC P1371 is not present and a no start condition is present, Refer to Engine Cranks But Does Not Run .

• | For intermittents, refer to Symptoms .

### Test Description

Number(s) below refer to step numbers on the diagnostic table.

1. This step verifies if the malfunction is active. If the engine starts, the malfunction is not present at this time.

2. If the harness and connections check out OK, but the engine stalls after reaching higher operating temperatures, return to Step 2 and test the system while the fault is present.

3. Normal voltage may vary slightly from the specified value. A value that is significantly higher or lower indicates a problem. This step isolates the circuit between the test connector and the PCM.

4. Normal voltage may vary slightly from the specified value. A value that is significantly higher or lower indicates a problem. This step isolates the circuit between the test connector and the distributor.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 |

1. Install the scan tool.
2. Using the scan tool, monitor Engine Speed.
3. Crank the engine.

Does the scan tool indicate RPM while cranking the engine?

--

Go to Step 3

Go to Step 4

3 |

1. Start the engine.
2. With the engine running, move related harnesses and connectors between the distributor and the PCM.

Does the engine cut out or stall while moving the various components.

--

Go to Step 4

Go to Diagnostic Aids

4 |

1. Turn the ignition OFF.
2. Disconnect the ignition system test connector.
3. Turn the ignition ON, use a DVM (J 39200) on DC volts scale, measure voltage on terminal A at the PCM side of the ignition test connector.

Does the DVM indicate the voltage specified?

5 V

Go to Step 5

Go to Step 8

5 |

1. Turn the ignition OFF.
2. Reconnect the ignition system test connector.
3. Disconnect Distributor connector.
4. Turn the ignition ON, use a DVM (J 39200) on DC volts scale, measure voltage on terminal A of Distributor electrical connector.

Does the DVM indicate voltage specified?

5 V

Go to Step 11

Go to Step 6

6 | Is voltage higher than the specified value? | 5 V | Go to Step 7 | Go to Step 12
7 | Repair the short to voltage on Low Resolution signal circuit from PCM to ignition system test connector. Is the action complete? | -- | Go to Step 15 | --
8 | Is the voltage higher than the specified value? | 5 V | Go to Step 10 | Go to Step 9
9 | Repair the open or grounded Low Resolution circuit from the ignition system test connector to the PCM. Was the condition found and repaired? | -- | Go to Step 15 | Go to Step 14
10 | Repair the short to voltage on Low resolution signal circuit from ignition system test connector to Distributor. Is the action complete? | -- | Go to Step 15 | --
11 | Repair the faulty Distributor connection or faulty Distributor. Is the action complete? | -- | Go to Step 15 | --
12 | Repair the open or grounded Low Resolution circuit from ignition system test connector to the Distributor. Was the condition found and repaired? | -- | Go to Step 15 | Go to Step 14
13 | Repair the harness/connections as necessary. Is the action complete? | -- | Go to Step 15 | --
14 | Important:: Replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Is the action complete? | -- | Go to Step 15 | --
15 |

1. Using the scan tool, select DTC, Clear Info.
2. Start the engine and idle at normal operating temperature.
3. Select DTC, Specific, then enter the DTC number which was set.
4. Operate the vehicle within the conditions for setting this DTC as specified in the supporting text, if applicable.

Does the scan tool indicate that this test ran and passed?

--

Go to Step 16

Go to Step 2

16 | Using the scan tool, select Capture Info, Review Info. Are any DTCs displayed that have not been diagnosed? | -- | Go to the applicable DTC table | System OK