GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2002 🢒 Impala 🢒 Engine 🢒 Engine Controls - 3.8L 🢒 DTC P1374

Circuit Description

The 3X reference signal is produced by the ignition control module (ICM). The ICM calculates the 3X reference signal by dividing the crankshaft position (CKP) sensor 18X pulses by 3 when the engine is running and CKP sync pulses are also being received. The powertrain control module (PCM) uses the 3X reference signal to calculate engine RPM and crankshaft position at engine speeds above 1,200 RPM. The PCM also uses the pulses on this circuit to initiate injector pulses. The PCM constantly monitors the number of pulses on the 3X reference circuit and compares the number of 3X reference pulses to the number of 18X reference pulses and CAM signal pulses being received. The PCM will use the 18X reference signal circuit for fuel and ignition control. The engine will continue to start and run using the 18X reference and camshaft position PCM input signals only. If the PCM detects an incorrect number of pulses on the 3X reference circuit, DTC P1374 sets.

Conditions for Running the DTC

The engine is running for more than 3 seconds.

Conditions for Setting the DTC
    • The ratio of 18X reference pulses to CAM signal pulses received by the PCM equals 36:1.
    • The ratio of 18X reference pulses to 3X reference pulses received by the PCM does not equal 6:1.
    • The above conditions are present for up to 30 seconds.

Action Taken When the DTC Sets
    • The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
    • The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC
    • The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
    • A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
    • Clear the MIL and the DTC with a scan tool.

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module Connector End Views

1

Did you perform the Diagnostic System Check-Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

Attempt to start the engine.

Does the engine start and run?

Go to Step 3

Go to Step 4

3
  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Turn OFF the ignition.
  3. Start the engine.
  4. Operate the vehicle within the conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Does the DTC fail this ignition?

Go to Step 4

Go to Intermittent Conditions

4
  1. Turn OFF the ignition.
  2. Disconnect the ignition control module (ICM).
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp to battery voltage.
  5. Observe the engine speed parameter on the scan tool.
  6. Repeatedly touch the test lamp quickly to the low resolution engine speed signal circuit at the ICM harness connector.

Is an engine speed displayed?

Go to Step 8

Go to Step 5

5
  1. Inspect for the following conditions:
    2. • The low resolution engine speed signal circuit open
    • The low resolution engine speed signal circuit shorted to ground
    • The low resolution engine speed signal circuit shorted to voltage
  2. If a condition is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 11

Go to Step 6

6

Test for an intermittent and for a poor connection at the PCM. Refer to Testing for Continuity , Testing for Intermittent Conditions and Poor Connections , Repairing Connector Terminals , and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 11

Go to Step 7

7

Inspect for the following conditions:

    • An incorrect harness routing near secondary ignition components
    • An ignition coil arcing to the wiring harness or to the ignition control module

       Important: If carbon tracking is detected on any component, replace that component and its mate.

    • Ignition coils for cracks, carbon tracking, or other signs of damage--Refer to Ignition Coil Replacement .
    • Secondary ignition wires arcing to the wiring harness--Refer to Spark Plug Wire Replacement .

Did you find and correct the condition?

Go to Step 11

Go to Step 10

8

Test for an intermittent and for a poor connection at the ICM. Refer to Repairing Connector Terminals in Wiring Systems .

Did you find and correct the condition?

Go to Step 11

Go to Step 9

9

Replace the ICM. Refer to Ignition Control Module Replacement .

Did you complete the replacement?

Go to Step 11

--

10

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

Go to Step 11

--

11
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

Go to Step 2

Go to Step 12

12

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

Go to Diagnostic Trouble Code (DTC) List

System OK