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HOMESERVICE MANUALSCHEVROLET2006CHEVY EXPRESS G2500, VAN CARGO, 6.6 2REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 1577 (POWER TAKE-OFF SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESDTC P251A-P251FCIRCUIT/SYSTEM TESTING
2006 Chevrolet Chevy Express G2500, Van Cargo, 6.6 2

Circuit/System Testing

2006 Chevrolet Chevy Express G2500, Van Cargo, 6.6 2SECTION Circuit/System Testing
WARNING: This page is about a different car, the 2009 GMC Sierra, 2009 GMC Cab & Chassis Sierra, and 2009 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.

P251A

  1. Ignition OFF, disconnect the harness connector at the PTO module.
  2. Ignition OFF, disconnect the harness connector at the in-cab PTO switch.
  3. Ignition OFF, test for infinite resistance between the harness connector at the PTO switch mode select A signal circuit terminal 2 and ground.
    • If less than the specified value, test the mode select A signal circuit for a short to ground.
  4. Ignition OFF, test for less than 1.0 ohm of resistance in the mode select A signal circuit between the PTO switch connector terminal 2 and the PTO module connector terminal 26.
    • If greater than the specified range, test the mode select A signal circuit for an open/high resistance.
  5. Ignition OFF, test for infinite resistance between the harness connector at the PTO switch mode select B signal circuit terminal 9 and ground.
    • If less than the specified value, test the mode select B signal circuit for a short to ground.
  6. Ignition OFF, test for less than 1.0 ohm of resistance in the mode select B signal circuit between the PTO switch connector terminal 9 and the PTO module connector terminal 11.
    • If greater than the specified range, test the mode select B signal circuit for an open/high resistance.
  7. Ignition OFF, test for infinite resistance between the harness connector at the PTO switch mode select C signal circuit terminal 4 and ground.
    • If less than the specified value, test the mode select C signal circuit for a short to ground.
  8. Ignition OFF, test for less than 1.0 ohm of resistance in the mode select C signal circuit between the PTO switch connector terminal 4 and the PTO module connector terminal 12.
    • If greater than the specified range, test the mode select C signal circuit for an open/high resistance.
  9. If all circuits test normal, replace the PTO switch.

P251E or P251F

  1. Ignition OFF, disconnect the harness connector at the PTOM.
  2. Ignition ON, test for 0 volts between the PTO engine shutdown signal circuit terminal 33 and ground.
    • If greater than the specified value, test the PTO engine shutdown signal circuit for a short to voltage. If the circuit test normal, replace the ECM.
  3. Ignition OFF, disconnect the harness connector X1 at the ECM.
  4. Ignition OFF, test for infinite resistance between the PTO engine shutdown signal circuit X1 terminal 84 and ground.
    • If less than the specified range, test the PTO engine shutdown signal circuit for a short to ground.
  5. Ignition OFF, test for less than 1.0 ohm on the PTO engine shutdown signal circuit between the PTO connector terminal 33 and the ECM connector X1 terminal 84.
    • If greater than the specified range, test the PTO engine shutdown signal circuit for an open/high resistance.
  6. Ignition OFF, test for less than 1.0 ohm on the PTO engine shutdown signal circuit between the PTO connector terminals 33 and 31.
  7. If greater than the specified range, test the PTO engine shutdown signal circuit for an open/high resistance. If the circuit tests normal, test or replace the upfitter remote switch assembly.
  8. If all circuits test normal, replace the PTOM.
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Stop DIY work and contact a certified mechanic immediately if any of the following apply:

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  • • 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.