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HOMESERVICE MANUALSISUZU2006ASCENDER S, 5.3 M, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 12 (BATTERY, CHARGING SYSTEM AND STARTING SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESDTC P1638: GENERATOR F-TERMINAL CIRCUITTEST DESCRIPTION
2006 Isuzu Ascender S, 5.3 M, 4WD

Test Description

2006 Isuzu Ascender S, 5.3 M, 4WDSECTION Test Description
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2004 Oldsmobile Bravada, 2004 GMC Envoy XUV, 2004 GMC Envoy XL, 2004 GMC Envoy, and 2004 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.
DTC P1638

Step Action Value(s) Yes No
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, observe the GEN - F Terminal parameter in the PCM data list.
Does the scan tool indicate that the GEN - F Terminal parameter is within the specified range?		 5-95% Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems Go to Step 3 
3
  1. Turn ON the ignition, leaving the engine OFF.
  2. Connect a test lamp to battery positive voltage and repeatedly probe the generator field duty cycle signal circuit in the harness connector while monitoring the Generator PWM on the scan tool.
Is the Generator PWM display affected?		 - Go to Step 5  Go to Step 4 
4 Test the generator field duty cycle 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 
6 Inspect for poor connections at the harness connector of the powertrain control module (PCM). Refer to Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 8  Go to Step 7 
7 Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement in Engine Controls - 5.3L or to Powertrain Control Module (PCM) Replacement in Engine Controls - 4.2L.
Is the action complete?		 - Go to Step 8  -
8
  1. Review and record the scan tool Failure Records data.
  2. Clear any DTCs.
  3. Operate the vehicle within the Failure Records conditions as noted.
  4. Using a scan tool, monitor the Specific DTC info for this DTC.
Does the scan tool indicate that this DTC failed this ignition?		 - 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.