Code
P1280
PONTIAC
P — Powertrain
Open Or Shorted Condition Detected In The Fuel System Relay Control Circuit
AI status
Completed
Completed
100%
Causes
- Blown fuse for fuel relay or related circuit
- Failed fuel system relay (coil or contacts)
- Open, shorted or damaged wiring between relay and PCM
- Corroded, loose or damaged relay/connector pins
- Poor or missing ground in relay/control circuit
- PCM output driver fault or internal short
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated
- Engine cranks but does not start (no fuel pump operation)
- Intermittent stalling or no-start conditions
- No audible fuel pump prime on key-on
- Possible drivability problems when relay control is intermittent
What to check
- Retrieve freeze frame and related pending codes; clear codes and attempt to reproduce
- Visually inspect fuses, fuel relay, relay socket and wiring for damage or corrosion
- Check for audible fuel pump prime at key-on
- Backprobe relay control and power terminals while performing key-on and crank tests
- Inspect ground points related to fuel system and PCM
- Substitute a known-good relay (if available) to rule out a bad relay
Signal parameters
- Battery voltage present at relay power feed: approx. 11–14 V (key-on, engine running)
- Relay coil resistance (typical small automotive relay): roughly 70–150 ohms (varies by relay)
- Control terminal behavior: expected to change state when PCM commands relay (either pulled to ground or switched to battery depending on vehicle design)
- Continuity relay control pin to PCM control pin: near 0 ohms (low resistance) if intact; open = infinite/very high resistance
- No short to battery or permanent ground on control circuit when relay is not commanded
Diagnostic algorithm
- Verify code P1280 and check freeze-frame/vehicle history; note conditions when fault set (key-on, crank, running).
- Perform visual inspection of relay, relay socket, related fuses, and wiring harness for damage, corrosion, or disconnected connectors.
- With key-off, measure relay coil resistance (remove relay) and compare to typical range; replace relay if coil open or shorted.
- Backprobe relay connector power terminal: verify battery voltage with key-on; if missing, trace feed and check fuses/ignition circuits.
- Backprobe relay control terminal while a helper turns key to ON/START: observe voltage behavior. Determine whether PCM switches control to ground or to battery; record voltages.
- If control signal does not change, check continuity between relay control terminal and PCM control pin. Repair open circuits, chafed wires, or poor terminals.
- If control circuit is shorted to battery or ground, isolate and repair short (disconnect sections of harness to pinpoint).
- If wiring and relay test good but PCM does not command the circuit when it should, verify inputs to PCM (crank/start signals, immobilizer status). Only after all wiring and component tests confirm should the PCM be considered faulty.
- Clear codes and retest to confirm repair; road test and monitor for return of DTC.
Likely causes
- Blown EFI or fuel pump fuse
- Faulty fuel system relay (coil open or shorted)
- Open/shorted control wire between relay socket and PCM pin (chafing, connector fault)
- Corroded relay socket or poor pin contact at relay/PCM connector
- Aftermarket alarm/immobilizer or previous repairs incorrectly wired into relay feed
- PCM driver failure (least common)
Fault status
Status
Open or short detected in fuel system relay control circuit — PCM cannot properly control the fuel system relay.
Repair difficulty: Medium
Diagnostic time: 0.5-2 hours
Similar codes
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
0
👎 Dislike
0
Send to email