The 1994 Buick Roadmaster, a classic full-size car, utilizes the OBD2 (On-Board Diagnostics II) system for diagnosing engine and other vehicle issues. Understanding these diagnostic trouble codes (DTCs) is crucial for effective troubleshooting and repair. This comprehensive guide provides a detailed list of OBD2 codes specific to the ’94 Roadmaster, categorized by system.
Decoding PCM (Powertrain Control Module) Trouble Codes (-00)
The PCM monitors the engine and transmission, managing vital functions like fuel injection and ignition timing. Here are common PCM codes for the ’94 Roadmaster:
- Code 13: Bank 1 (left) heated oxygen sensor (O2) – open circuit. Indicates a problem with the oxygen sensor’s wiring or the sensor itself.
- Code 14: Engine coolant temperature (ECT) sensor – signal voltage low (high temperature indicated). Suggests a faulty ECT sensor, wiring issue, or low coolant level.
- Code 15: ECT sensor – signal voltage high (low temperature indicated). Opposite of Code 14, pointing to similar potential causes.
- Code 21: Throttle position sensor (TPS) – signal voltage high. Indicates a problem with the TPS, its wiring, or the throttle body.
- Code 22: TPS – signal voltage low. Similar to Code 21, but with low voltage instead of high.
- Code 23: Intake air temperature (IAT) sensor – signal voltage high (low temperature indicated). Suggests a faulty IAT sensor or wiring issue.
- Code 24: Vehicle speed sensor (VSS) circuit. Indicates a problem with the VSS, its wiring, or the sensor’s connection.
- Code 25: IAT sensor – signal voltage low (high temperature indicated). Opposite of Code 23, with similar potential problems.
- Code 32: Exhaust gas recirculation (EGR) system. Points to a fault within the EGR system, potentially the valve, solenoid, or related components.
- Code 33: Manifold absolute pressure (MAP) sensor – signal voltage high (vacuum low). Suggests a vacuum leak, faulty MAP sensor, or wiring problem.
- Code 34: MAP sensor – signal voltage low (vacuum high). Opposite of Code 33, indicating a potential blockage or faulty sensor.
- Code 43: Knock sensor (KS) circuit. Indicates a malfunctioning knock sensor, wiring issue, or excessive engine noise.
- Code 44: Bank 1 (left) heated O2 sensor – lean exhaust indicated. Suggests a lean fuel mixture or a problem with the O2 sensor.
- Code 45: Bank 1 (left) heated O2 sensor – rich exhaust indicated. Indicates a rich fuel mixture or a faulty O2 sensor.
Other System Diagnostic Trouble Codes
The ’94 Roadmaster has other modules besides the PCM:
- CCM (Climate Control Module) (-01): Manages the heating, ventilation, and air conditioning system. Codes relate to sensor failures, actuator problems, and communication errors.
- HVAC (Heating, Ventilation, and Air Conditioning) (-02): Similar to CCM, codes address temperature sensor issues, communication problems, and EEPROM errors.
- SIR (Supplemental Inflatable Restraint) (-03): Controls the airbag system. Codes indicate deployment loop issues, sensor malfunctions, and crash data.
- ABS/TC (Anti-lock Brake System/Traction Control) (-04): Manages braking and traction control. Codes pertain to wheel speed sensor problems, valve solenoid malfunctions, and system voltage issues.
Utilizing OBD2 Codes for Diagnosis
These codes are a starting point for diagnosing problems. Further inspection, testing with a scan tool, and referencing a repair manual are crucial for accurate diagnosis and repair of your 1994 Buick Roadmaster. A professional mechanic can provide expert assistance in interpreting these codes and resolving underlying issues.
