Code 55
Code 55 is a diagnostic trouble code related to the ECM on the Pontiac Fiero.
Code 55 indicates that the ECM has detected an internal error or serious ECM-related fault.
Overview
The ECM controls the engine management system. It receives sensor inputs, processes engine operating conditions, and controls fuel delivery, ignition timing, idle control, emissions functions, and diagnostic functions.
Code 55 is set when the ECM detects an internal problem or a serious fault related to ECM operation.
Because Code 55 points toward the ECM itself, it should be diagnosed carefully. Power, ground, wiring, connectors, charging voltage, PROM, CALPAK, and related electrical issues should be checked before assuming the ECM has failed.
Flash pattern
Code 55 is displayed as:
- Five flashes
- Pause
- Five flashes
This represents code 55.
Animated flash pattern:
Meaning
Code 55 usually indicates an ECM error.
Possible causes include:
- Faulty ECM
- ECM power problem
- ECM ground problem
- Poor ECM connector contact
- Corroded ECM terminals
- Internal ECM damage
- PROM or CALPAK problem
- Charging-system voltage problem
- Electrical short or wiring fault
- Water damage
- Previous ECM modification or repair
Symptoms
Possible symptoms may include:
- Check engine light
- No-start condition
- Stalling
- Engine runs poorly
- Poor idle
- Intermittent shutdown
- Erratic sensor readings
- Multiple unrelated trouble codes
- Poor drivability
- Little or no obvious drivability problem in some cases
Diagnosis
Basic diagnostic checks include:
- Confirm that Code 55 is present.
- Check for other stored trouble codes.
- Inspect ECM connectors.
- Check ECM power feeds.
- Check ECM grounds.
- Inspect wiring for damage or previous repairs.
- Check battery and charging-system voltage.
- Check for signs of water intrusion or corrosion.
- Check PROM and CALPAK seating if the ECM has been opened.
- Consider ECM replacement only after power, ground, wiring, connector, PROM, CALPAK, and voltage issues have been checked.
ECM power and grounds
The ECM depends on clean power and good grounds. Poor power supply, weak grounds, or corroded connections can cause ECM-related symptoms and may set ECM fault codes.
Related topics:
PROM and CALPAK
PROM or CALPAK issues may cause ECM-related trouble codes or poor engine operation. These parts should be checked if the ECM has been opened, modified, or replaced.
Related topics:
Related codes
Related ECM and voltage codes include:
Notes
Code 55 should not automatically be treated as proof that the ECM is bad. Poor power, poor grounds, connector problems, voltage problems, PROM issues, CALPAK issues, and wiring faults can all cause ECM-related problems.
If all external causes are ruled out and Code 55 returns, ECM replacement or repair may be necessary.