Code
P1581
HUMMER
P — Powertrain
Cruise Move Circuit High Voltage
AI status
Completed
Completed
100%
Causes
- Short to battery voltage on the cruise move circuit (wiring harness damage or pin contact)
- Faulty cruise actuator/motor or internal short in actuator electronics
- Corroded or damaged connector terminals causing abnormal voltage reading
- Faulty relay or fused power feed supplying the cruise circuit
- Body/Powertrain Control Module (BCM/PCM) output driver fault
- Aftermarket electrical modifications or jump-start wiring errors
Symptoms
- Cruise control will not engage or disengages unexpectedly
- Cruise set/unset warning on dash or lamp illuminated
- Stored P1581 code and possibly other cruise/throttle-related codes
- Erratic or unresponsive throttle/cruise actuation
- Possible illumination of MIL (check engine light)
What to check
- Read stored freeze-frame and pending codes with a scan tool; note freeze-frame conditions
- Visual inspection of cruise actuator, related wiring harnesses and connectors for damage, corrosion, or pin pushed out
- Inspect fuses and relays for the cruise/power supply circuit
- Measure battery voltage to confirm stable supply (engine off and running)
- Backprobing connector at cruise actuator to measure circuit voltage under key ON and during attempted activation
- Perform wiggle test on harness while monitoring voltage/scan data to reproduce the fault
Signal parameters
- Battery voltage (expected): ~11–14.5 V depending on key/engine state
- Cruise move circuit expected: approximately battery voltage when power feed is applied; fault triggers when measured voltage is higher than allowable threshold or abnormal compared to reference
- Trigger condition: cruise circuit voltage significantly above expected range or showing unexpected constant battery feed when it should be switched
- Control signal type: vehicle-specific (switched 12V supply or module-driven); consult model service data for exact waveform and thresholds
Diagnostic algorithm
- Connect a scan tool. Record P1581, related codes, and freeze-frame data. Clear codes and attempt to re-run to confirm reproducibility.
- Visually inspect all wiring and connectors between the cruise actuator, switches, fuse/relay box, and the vehicle control module. Repair any chafing, corrosion, or damaged terminals.
- With ignition ON (engine off) and using a digital multimeter, measure voltage at the cruise actuator power pin and reference ground. Note voltage at rest and while operating the cruise command (use an assistant or scan tool command).
- If voltage is higher than battery or behaves abnormally, disconnect the actuator connector and measure voltage at the harness side. If the harness side still shows high voltage, suspect power feed/relay or short to B+. If voltage drops, suspect actuator internal short.
- Inspect and test related relay(s) and fuses. Replace suspect relay and retest.
- If wiring and power feed are OK, bench-test or replace the cruise actuator per service procedures. Reinstall and verify operation.
- If actuator and wiring are good, test the control module output circuits using service diagnostic flowcharts; consider module replacement only after confirming external circuitry is correct.
- After repairs, clear codes and perform a road test to confirm the fault does not return. If intermittent, perform longer monitoring with scan tool.
Likely causes
- Damaged insulation or chafed wiring shorted to B+ feeding the cruise move circuit
- Failed cruise actuator with internal short to power
- Loose/corroded connector causing intermittent high voltage feedback
- Stuck or welded relay supplying continuous battery voltage to circuit
- Controller driver transistor failed and is sourcing incorrect voltage
Fault status
Status
Stored when the cruise control 'move' circuit voltage is detected above the allowed threshold or behaves abnormally compared with expected supply/reference voltage.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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