Code
C1214
HUMMER
C — Chassis
System Relay Contact or Coil Circuit Open
AI status
Completed
Completed
100%
Causes
- Blown or open relay coil
- Broken or corroded relay contacts
- Blown fuse or fusible link feeding the relay
- Open or shorted wiring between relay, power source and control module
- Poor or missing ground at relay or control module
- Faulty control module driver (ECM/ABS/BCM) that energizes the relay
Symptoms
- Related system inoperative (ABS, traction control, transfer case, fuel pump or other system powered by that relay)
- Warning lamp(s) illuminated on the dash (ABS, traction, service, or system-specific light)
- No clicking sound from relay when system attempts to energize
- Intermittent or permanent loss of system function
- Possible no-crank/no-start if relay supplies starter or fuel circuit
What to check
- Read and record all stored codes and freeze-frame data with a scan tool; check pending/history
- Verify battery voltage is healthy (12.4–12.8 V resting, >13.5 V with engine running)
- Visually inspect relay, relay socket, associated fuses and wiring for damage, corrosion, or water
- Listen for relay click when commanded; if absent, test coil and control signal
- Swap relay with an identical known-good relay (if available) to quickly check relay function
- Measure relay coil resistance and contact continuity with a multimeter
Signal parameters
- Battery supply to relay common terminal: ~12 V (key ON) or battery voltage
- Relay coil control voltage: 0 V (inactive) to ~12 V (active) depending on module drive style
- Typical small automotive relay coil resistance: ~50–200 Ω (varies by relay type); large power relays or latching relays may be higher
- Contact continuity: near 0 Ω when relay is energized; open/infinite Ω when de-energized
- Voltage at relay contact output when energized: ~battery voltage minus small voltage drop (
Diagnostic algorithm
- Verify the code and note conditions (key on, engine running, ABS active, etc.). Record any related codes.
- Check battery voltage and main fuses. Replace any blown fuses before further testing.
- Visually inspect the relay and socket for corrosion, melting, or water. Replace the relay if suspicious.
- With ignition OFF, measure coil resistance across the relay coil terminals (compare to spec or swap relay).
- With ignition ON, backprobe the relay coil supply terminal and the control terminal. Have an assistant activate the system while watching for control voltage change. If supply is present but control never energizes, suspect module/driver or wiring to module.
- If coil energizes but load side is not powered, check continuity across the relay contacts when energized. If coil energizes but contacts stay open, replace the relay.
- If coil never energizes and no control voltage from module, trace continuity of the control and supply wires back to the module and fuses. Repair any open or shorted wiring and restore proper grounds.
- If wiring and relay are good but the control output is absent, suspect the controlling module (ECM/ABS/BCM). Verify module grounds and power; consult service information before replacing module.
- After repairs, clear codes, perform relearns/self-tests if required, and verify system operation on a road test or activation test.
Likely causes
- Failed relay (most common)
- Blown fuse supplying the relay
- Open control wire from module to relay coil
- Disconnected or corroded relay socket terminal
- Low battery or weak supply preventing proper relay activation
Fault status
Status
System Relay Contact or Coil Circuit Open — relay coil not energizing or contacts not closing; related system may be disabled.
Repair difficulty: Medium
Diagnostic time: 0.5-2 hours
Similar codes
Repair manuals
Manual library for HUMMER
138
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