Code
P0362
HUMMER
P — Powertrain
Ignition Coil L Primary/Secondary Circuit Malfunction
Views:
UK: 13
EN: 24
RU: 16
AI status
Completed
Completed
100%
Causes
- Faulty ignition coil (coil L)
- Damaged wiring or harness (open, short to ground or power, high resistance)
- Poor or corroded connector/terminal at coil
- Faulty ignition driver in PCM/ECM or ignition control module
- Intermittent connection from vibration or heat
- Low battery/charging system voltage or poor ground
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated
- Rough idle or engine misfire at idle or under load
- Reduced engine power, hesitation or stumble
- Poor fuel economy
- Intermittent starting or stalling in severe cases
What to check
- Scan for freeze frame data, related P-codes and pending codes
- Visually inspect coil L, connector and harness for damage, corrosion or loose pins
- Verify battery and charging system voltage (stable ~12.6 V at rest, >13.5 V running)
- Backprobe coil connector and observe primary signal with a lab scope or digital voltmeter
- Measure coil primary and secondary resistance (compare to spec)
- Swap coil L with a known-good coil of the same type to see if code follows
Signal parameters
- Primary circuit resistance: typically ~0.3–2.0 Ω (manufacturer-specific — consult service data)
- Secondary circuit resistance: typically ~5 kΩ–15 kΩ (varies by coil design)
- Primary voltage pulses: switching from battery voltage to ground; expect pulses near battery voltage with rapid transitions when cranking/idle
- Primary current pulses: coil primary currents can peak several amps (spec varies), expect pulsed current rather than steady
- Waveform: primary shows sharp square/triangular pulses with duration (dwell) controlled by PCM — pulse frequency increases with RPM
- No primary or abnormal/flat waveform indicates open circuit or driver failure; constant battery on/short-to-power indicates short
Diagnostic algorithm
- Retrieve codes and freeze frame data with a scan tool; note engine RPM, load and voltage when fault set.
- Visually inspect coil L, connector and wiring for damage, corrosion, melted insulation or oil contamination. Repair any obvious issues.
- Check battery and charging system voltage. Low voltage can cause false coil DTCs.
- With ignition off, disconnect coil connector and measure primary and secondary resistance of the coil. Compare to manufacturer spec. If out of range, replace coil.
- Reconnect and backprobe coil primary terminal. Crank/run engine and observe waveform with lab scope. Look for pulsed signal at PCM driver. No pulses may indicate open circuit or failed driver.
- If no primary pulses but coil has correct resistance, check continuity and resistance from coil connector to PCM driver pin and check for shorts to battery or ground.
- Swap coil L with another cylinder's identical coil. If code follows the coil, replace coil. If code stays with same position, suspect wiring or PCM driver.
- If wiring and coil check good, test/replace PCM or ignition control module only after confirming driver is faulty and following service manual procedures.
- After repairs, clear codes and perform a road/test cycle to verify code does not return and that misfire symptoms are resolved.
Likely causes
- Internal short/open within coil L (most common)
- Corroded/loose coil connector or pinned terminal
- Broken wire or damaged insulation near coil harness
- PCM driver fault (less common) or intermittent solder joint
- Aftermarket coil with incorrect specifications
Fault status
Status
PCM detected a malfunction in the primary or secondary circuit of ignition coil L. This can trigger a misfire, reduced power and MIL illumination. Investigation of coil, wiring, connectors and PCM driver required.
Repair difficulty: Medium
Diagnostic time: 0.5-3 hours
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