Code
P0601
HUMMER
P — Powertrain
Control Module Read Only Memory (ROM)
AI status
Completed
Completed
100%
Causes
- Failed or incomplete PCM/ECM reflash or software update
- Corrupted ROM contents due to internal failure
- Battery voltage loss or low voltage during programming
- Manufacturing or part defect in the control module
- Water intrusion, corrosion, or physical damage to the module
- Faulty power or ground circuits to the control module
Symptoms
- Check Engine MIL illuminated (CEL)
- Engine will run poorly, enter limp mode, or not start
- Loss of communication with PCM on scan tool or intermittent responses
- Multiple control-module related DTCs or network U-codes present
- Unexpected drivability issues after a recent software update or module replacement
What to check
- Read and record all stored DTCs and freeze-frame data with a CAN-capable scan tool
- Verify battery state-of-charge and charging system voltage (should be 12.4–14.8 V during diagnosis)
- Check for related communication (U) codes that indicate wiring or bus issues
- Visually inspect PCM/ECM for water damage, corrosion, physical damage, and secure mounting
- Inspect power, ground, and connector pins for corrosion, loose terminals, or broken wires
- Confirm software/part numbers and calibration IDs in the module match vehicle build and VIN records
Signal parameters
- PCM supply voltage during scans (nominal 12–14.8 V)
- Module respond rate to scan tool queries (present / intermittent / no response)
- Stored PCM software part number and calibration ID (should match manufacturer specification)
- Checksum or verification status reported by reprogramming tool (pass/fail)
- Related network traffic on CAN (normal / errors present)
Diagnostic algorithm
- Retrieve and record all DTCs, freeze frame, and related U-codes. Note recent history of reprogramming or module replacement.
- Verify good battery charge and stable voltage. Recharge or connect a battery maintainer before any reflash attempt.
- Inspect PCM connector, pins, power and ground circuits for corrosion, damage, or loose connections. Repair any wiring faults.
- Clear codes and attempt to reproduce. If P0601 returns immediately or intermittently, proceed to programming checks.
- Confirm VIN, part number, and calibration IDs using manufacturer scan tool. Compare to factory data/TSBs.
- Attempt a reflash/restore of PCM ROM using the correct manufacturer tooling, firmware, and procedures. Ensure uninterrupted power during the operation.
- If reflash fails or reports ROM failure, test/replace wiring peripherals (ignition switch, power distribution) that could interrupt programming, then retry.
- If module still cannot be repaired by reprogramming or reports internal ROM fault, follow manufacturer instructions for module replacement and required vehicle/module coding/learning procedures.
- After repair/reprogram, clear codes and verify proper operation, communications, and that no related codes return. Document software levels and actions taken.
Likely causes
- Internal ROM corruption inside PCM/ECM
- Improper/incomplete dealer or aftermarket reprogramming
- Interruption of battery power while flashing software
- Damaged connector pins or wiring to PCM causing memory errors
- Previous repair used wrong software/part number for module
Fault status
Status
ROM memory verification failed or ROM image corrupted in the control module. Module software checksum or calibration ID invalid; reprogramming or module replacement likely required.
Repair difficulty: Hard
Diagnostic time: 1-4 hours
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Repair manuals
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138
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