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HOMESERVICE MANUALSCHEVROLET1999PICKUP C2500, 2D PICKUP, 6.5 F, STANDARDREPAIR AND DIAGNOSISENGINE PERFORMANCESYSTEMENGINE CONTROL SYSTEM - TESTS W/CODES - DTC P0352-P0452DTC P0372DTC P0372: IGNITION CONTROL (IC) MODULE 24X REFERENCE CIRCUIT-MISSING PULSES (4.0L "G" BODY & 4.6L "E" & "K" BODIES)DIAGNOSTIC PROCEDURES
1999 Chevrolet Pickup C2500, 2D Pickup, 6.5 F, Standard

Diagnostic Procedures

1999 Chevrolet Pickup C2500, 2D Pickup, 6.5 F, StandardSECTION Diagnostic Procedures
  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS INTRODUCTION article. After performing OBD system check, go to next step.
  2. Using scan tool, verify if DTC P1323 is also present. If DTC P1323 is present, diagnose this DTC first. If DTC P1323 is not present, go to next step.
  3. Turn ignition off. Disconnect IC module harness connector C4. Using 6-Pin IC Module Diagnostic Jumpers, jumper the following IC module connector C4 terminals to the following module terminals:
    • C4 Terminal "A" To Module Pin "A"
    • C4 Terminal "B" To Module Pin "B"
    • C4 Terminal "C" To Module Pin "C"
    • C4 Terminal "D" To Module Pin "D"
    • C4 Terminal "E" To Module Pin "E"
    • C4 Terminal "F" To Module Pin "F"
    Set DVOM to 400 mV AC scale and push Hz button. Connect DVOM between terminal "A" jumper and ground. Start engine and check frequency. If frequency is 200 Hz or greater, go to next step. If frequency is not 200 Hz or greater, go to step  5.
  4. Check terminal contact for 24X spark reference circuit at PCM connector C2. Check 24X reference circuit between PCM and IC module harness connectors. Repair as necessary. If terminal contact and circuit are okay, go to step  10.
  5. Turn ignition on. Disconnect all jumpers. Turn ignition on. Using DVOM, check voltage between ground and cam low circuit terminal at IC module connector C4. If voltage reading is greater than 4.2 volts, go to next step. If voltage reading is not greater than 4.2 volts, go to step  8.
  6. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Reconnect IC module harness connector C4. Turn ignition on. Using DVOM, check voltage between ground and 24X spark reference circuit at PCM harness connector C2. Voltage reading should be 4.2 volts. If voltage reading is greater than 4.2 volts, go to step  4. If voltage reading is not greater than 4.2 volts, go to next step.
  7. Repair short to ground in 24X spark reference circuit.
  8. Check terminal contact of cam signal circuit at IC module harness connector C4. Repair as necessary. If circuit is okay, go to next step.
  9. Replace IC module.
  10. Replace PCM. Program replacement PCM using required equipment.
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.