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Home >> GMC >> 1999 >> Forward Control 6.5 Y, Automatic >> Repair and Diagnosis >> Accessories & Equipment >> Gauges & Instrument Panels >> Instrument Panel - Analog - P Series >> System Tests >> Fuel Gauge Always Reads Full (Gasoline)

Fuel Gauge Always Reads Full (Gasoline)

  1. Turn ignition off. Disconnect Vehicle Control Module (VCM) connector C1. Turn ignition on. Check voltage between VCM cavity C1 terminal No. 9 (Purple wire) and ground. If less than 10 volts exists, go to next step. If voltage is 10 volts or more, go to step  3.
  2. Repair open or short to ground on Purple wire between VCM connector C1 terminal No. 9 and instrument panel connector terminal No. 16. Recheck system.
  3. Using a fused jumper wire, connect VCM cavity C1 terminal No. 9 (Purple wire) to ground. Turn ignition on. If fuel gauge reads full, go to next step. If fuel gauge does not read full, go to step  6.
  4. Turn ignition off. Disconnect instrument panel connector. Check resistance of Purple wire between VCM connector C1 terminal No. 9 and instrument panel connector terminal No. 16. If resistance is more than one ohm, go to next step. If resistance is one ohm or less, go to step  10.
  5. Repair open on Purple wire between VCM connector C1 terminal No. 9 and instrument panel connector terminal No. 16. Recheck system.
  6. Turn ignition off. Disconnect VCM connector C3. Check resistance between connector C3 terminals No. 13 (Purple wire) and No. 19 (Black wire). If resistance is 40-250 ohms, go to next step. If resistance is not 40-250 ohms, go to step  8.
  7. Replace VCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE.
  8. Disconnect fuel pump module. Check resistance between fuel pump module connector cavities "A" and "D". If resistance is 40-250 ohms, go to next step. If resistance is not 40-250 ohms, go to step  11.
  9. Repair open on Purple wire between VCM connector C3 terminal No. 13 and fuel pump module connector terminal "A" or Black wire between VCM connector C3 terminal No. 19 and fuel pump module connector terminal "D". Recheck system.
  10. Replace instrument panel cluster. Recheck system.
  11. Replace fuel pump module. Recheck system.
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