Code
P0332
HUMMER
P — Powertrain
Knock Sensor 2 Circuit Low Input (Bank 2)
AI status
Completed
Completed
100%
Causes
- Faulty knock sensor (Bank 2, sensor 2)
- Short to ground in the knock sensor signal wire
- Poor or corroded connector or pin terminal at sensor or ECM
- Open circuit in sensor wiring
- Low/no reference or ground to the sensor
- Faulty ECM (less common)
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated
- Reduced power or engine in limp mode (timing retard)
- Perceived engine knock or pinging under load
- Poor fuel economy
- Rough idle or hesitation under some conditions
- Multiple knock-related or misfire-related codes may also appear
What to check
- Read and record freeze frame and live data with a scan tool; confirm P0332 is current
- Visually inspect the knock sensor, connector, and wiring on Bank 2 for damage or corrosion
- Wiggle the harness while monitoring scan tool data to check for intermittent changes
- Backprobe the sensor connector and measure signal at key engine conditions (idle and light load)
- Check continuity between sensor signal pin and ECM pin; check for short to ground
- Compare Bank 2 sensor signal to Bank 1 (if identical sensor) to see differences
Signal parameters
- Knock sensor is a piezo element that generates AC voltage pulses when detonation occurs; output is pulse-like rather than steady DC
- At no-knock idle the signal activity should be minimal; under load/knock the sensor produces voltage transients
- A 'low input' means the ECM sees signal voltage near 0 V or insufficient pulse amplitude
- Typical test methods: measure AC pulses with an oscilloscope during cranking/acceleration or monitor knock sensor voltage/frequency on a capable scan tool
- Resistance checks (if specified by service manual) only apply to certain sensor types—consult vehicle procedure before relying on resistance values
Diagnostic algorithm
- Verify the code: connect an OBD-II scan tool, read PIDs and freeze frame; note conditions when code set.
- Clear the code and perform a short drive cycle to see if P0332 returns. Intermittent faults may require extended testing.
- Visually inspect knock sensor (Bank 2) connector and wiring for corrosion, bent pins, heat damage, or chafing. Repair any obvious damage.
- With ignition on (engine off) check continuity between the sensor signal terminal and ECM signal pin; check for short to ground on the signal wire. Repair any opens/shorts.
- Backprobe the sensor signal while cranking and during a road test; monitor with a lab scope if available. Look for AC pulses under load. If signal is absent or stuck near 0 V, suspect sensor or wiring short to ground.
- If wiring and connectors are good, swap the Bank 2 knock sensor with the corresponding sensor on Bank 1 (if identical and reachable) and see if the code follows the sensor. If it does, replace the sensor.
- If the code remains on after sensor replacement and wiring is verified, inspect ECM connector for bent pins and perform ECM input diagnostics per service manual; consider ECM replacement only after all wiring/sensor checks are exhausted.
- After repair, clear codes and perform a full verification drive cycle and re-check for related codes and proper engine operation.
Likely causes
- Damaged or corroded connector at knock sensor
- Wiring chafed and shorted to engine ground
- Failed piezo knock sensor (age/heat damage)
- Connector pin pushed out or contaminated
- Harness repair/previous work left a poor splice
Fault status
Status
ECM detected low voltage/input from Knock Sensor 2 (Bank 2). Fault stored and MIL on.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
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Repair manuals
Manual library for HUMMER
138
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