Code
P1361
HUMMER
P — Powertrain
Ignition Coil Control Circuit Low Voltage
AI status
Completed
Completed
100%
Causes
- Open or high-resistance wiring between PCM and ignition coil control terminal
- Short to ground on the coil control circuit
- Failed ignition coil or coil pack (internal driver or winding)
- Bad connector, corrosion, or poor terminal contact at coil harness
- Weak battery or poor main power/ground affecting coil supply
- Blown fuse or poor PCM power/ground
Symptoms
- Check Engine Light with related DTC(s) stored
- Rough idle or engine misfire on affected cylinder(s)
- Reduced power, hesitation, or poor acceleration
- Hard starting or no-start in severe cases
- Increased fuel consumption or failed emissions test
What to check
- Read stored codes and freeze frame data with a scan tool; note which cylinder(s) are affected
- Visually inspect coil pack(s), harness and connectors for damage, corrosion, or oil contamination
- Check battery voltage and main engine grounds; ensure battery >= 12.4 V at rest and >= ~10 V while cranking
- Check ignition/ECM fuse(s) and power supply to coils
- Backprobe the coil control connector while cranking to observe voltage behavior (use appropriate test equipment)
- Perform wiggle test on wiring/connectors while engine is cranking/idle to reproduce fault
Signal parameters
- Idle/off: coil control terminal typically near battery voltage (~11–14 V) when driver is off
- Driver active: coil control is commonly a low-side switch — signal goes near 0 V (ground) during firing events
- Pulse frequency and duty vary with engine RPM and load (pulses per ignition event)
- Primary resistance (coil-dependent): commonly ~0.2–3 Ω; secondary resistance typically thousands of ohms (check OEM specs)
- Expected behavior: repeated pulses during cranking/running on the control circuit; no continuous low-level voltage that indicates short to ground
Diagnostic algorithm
- Safety: wear eye protection, disable ignition when disconnecting components; follow vehicle-specific safety procedures.
- Retrieve codes and freeze-frame; note cylinder(s) and related faults (misfires).
- Verify battery voltage and main grounds; recharge or load-test battery if low.
- Visually inspect coil(s), harness, and connectors for damage, corrosion, oil, or melted insulation.
- Check fuses and power feeds to coils and PCM; repair any blown fuses or open feeds.
- With connector connected, backprobe coil control lead. Crank engine and observe voltage: verify pulses that go near 0 V when driver grounds the circuit. If no pulses or voltage stuck low, proceed.
- Measure primary coil resistance against OEM spec. If out of spec, replace coil.
- Swap coils between cylinders (if coils are identical) to see if the DTC or misfire follows the coil.
- Check continuity and resistance of the wiring from the coil connector to the PCM; look for shorts to ground or battery and open circuits. Repair damaged wiring.
- If wiring and coils test good but the control output never switches, test the PCM driver output per service manual. Replace PCM only after confirming external wiring/coil failure is not present.
- Clear codes and test drive to confirm repair; monitor live data for coil control activity and misfire counts.
Likely causes
- Damaged/shorted wire at a harness edge or near the engine
- Corroded or loose coil connector terminals
- Failed ignition coil primary driver (internal to coil pack)
- Blown ignition/ECM fuse or weak battery under cranking load
- PCM output transistor failed
Fault status
Status
Ignition coil control circuit low voltage detected. PCM has sensed voltage below expected threshold on coil control circuit; may indicate open, short to ground, failed coil, wiring issue, or PCM driver fault.
Repair difficulty: Medium
Diagnostic time: 1–3 hours
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Repair manuals
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138
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