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OBD-II fault code definitions, symptoms, causes, and step-by-step diagnostics.
Standardized generic DTCComputer & output circuits

P0602 — Control Module Programming Error

P0602 is the standardized powertrain DTC for “Control Module Programming Error.” The code identifies the monitored condition; it does not by itself prove which part failed.

Standardized generic definition
Control Module Programming Error
DTC category
Computer & output circuits
Diagnostic priority
Moderate to high depending on symptoms. Module codes are often secondary to voltage, network, connector, or calibration problems.
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What P0602 means

P0602 is the standardized powertrain DTC for “Control Module Programming Error.” The code identifies the monitored condition; it does not by itself prove which part failed.

Start with the stored data and the simplest external checks before replacing the component named in the code.

Possible symptoms

  • Multiple warning lights
  • Intermittent no-start or limp mode
  • Communication loss
  • Unexpected module behavior

Causes to test

These are diagnostic possibilities, not a statistical parts-replacement ranking. Vehicle-specific service information takes priority.

  • Low/unstable system voltage
  • Power/ground or connector problem
  • CAN/network wiring fault
  • Incorrect or incomplete programming/calibration
  • Internal module fault

Step-by-step diagnostic workflow

  1. Stabilize and test battery/charging voltage before module replacement.
  2. Perform a full-vehicle module scan and identify which modules communicate.
  3. Check module power, grounds, fuses, and network termination/wiring.
  4. Review programming/calibration status and applicable service information.
  5. Replace/reprogram a module only after external causes are ruled out.
  6. Clear codes only after repair, then complete an appropriate drive cycle and verify the code and symptoms do not return.
Preserve evidence: EPA OBD guidance emphasizes that stored DTCs and freeze-frame data are important to proper diagnosis. Save them before clearing codes.

Scan data worth checking

  • Full module scan
  • System voltage
  • Network DTCs
  • Module software/calibration identifiers where supported

Severity and drivability

Moderate to high depending on symptoms. Module codes are often secondary to voltage, network, connector, or calibration problems.

Stop driving and investigate immediately if there is a flashing MIL, oil-pressure warning, overheating, fuel leakage, severe misfire, major loss of power, abnormal mechanical noise, or a transmission that is slipping badly.

Common diagnostic mistakes

  • Replacing a PCM/TCM based on a single internal code without power/ground checks
  • Ignoring low-voltage history
  • Programming a module without a stable power supply

Related generic codes

P0601 — Internal Control Module Memory Checksum ErrorP0603 — Internal Control Module Keep Alive Memory ErrorP0600 — Serial Communication Link MalfunctionP0604 — Internal Control Module Random Access Memory ErrorP0605 — Internal Control Module Read Only Memory ErrorP0606 — PCM/ECM Processor Fault

Source and accuracy notes

Generic DTC structure and standardized definitions are governed by SAE J2012/J2012DA. Actual enable criteria, thresholds, circuit pinouts, test values, software conditions, and repair procedures vary by vehicle. Use current OEM service information for the exact year/engine/calibration and check applicable manufacturer technical service bulletins. See the site methodology and primary-reference policy.