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HOMESERVICE MANUALSCHEVROLET2001C3500 HD 8.1 G, AUTOMATICREPAIR AND DIAGNOSISENGINE MECHANICALSTARTERBATTERY, CHARGING SYSTEM AND STARTING SYSTEMDIAGNOSTIC INFORMATION AND PROCEDURESDTC P1637CONDITIONS FOR CLEARING THE MIL/DTC
2001 Chevrolet C3500 HD 8.1 G, Automatic

Conditions for Clearing the MIL/DTC

2001 Chevrolet C3500 HD 8.1 G, AutomaticSECTION Conditions for Clearing the MIL/DTC
  • The DTC becomes history when the conditions for setting the DTC are no longer present.
  • The history DTC clears after 40 malfunction free warm-up cycles.
  • The PCM receives a clear code command from the scan tool.
DTC P1637

Step Action Value Yes No
Schematic Reference: Starting and Charging Schematics 
Connector End View Reference: Engine Electrical Connector End Views 
1 Did you perform the Engine Electrical Diagnostic System Check? - Go to Step 2  Go to Diagnostic System Check - Engine Electrical 
2
  1. Install a scan tool.
  2. Start the engine.
  3. With a scan tool, monitor the DTC information for DTC P1637 in Engine Controls.
Does the scan tool indicate that DTC P1637 has passed?		 - Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems Go to Step 3 
3
  1. Turn OFF the ignition.
  2. Disconnect the generator harness connector.
  3. Start the engine and let idle.
  4. Measure the voltage between the generator turn on signal circuit and ground.
Does the voltage measure near the specified value?		 10.0 V Go to Step 5  Go to Step 4 
4 Test the generator turn on signal circuit for a short or open. Refer to Circuit Testing , and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 8  Go to Step 6 
5 Inspect for poor connections at the harness connector of the generator. Refer to Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 8  Go to Charging System Test (CS/AD/SI Generators) 
6 Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections , and Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 8  Go to Step 7 
7
IMPORTANT:

The replacement PCM must be programmed.

Replace the PCM/ECM. Refer to: Powertrain Control Module Replacement , 4.3L, Powertrain Control Module Replacement , 4.8L/5.3L/6.0L, Powertrain Control Module Replacement , 8.1L or Engine Control Module Replacement 6.6L in Engine Controls.Is action complete?		 - Go to Step 8  -
8
  1. Use the scan tool in order to clear the DTCs .
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC reset?		 - Go to Step 2  System OK
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.