C0000: Vehicle Speed Information Circuit fault (commonly set when a steering-related control module does not receive a valid vehicle speed message over the vehicle network; in some generic code lists it is also shown as ISO/SAE reserved, so meaning can be manufacturer-implementation dependent).

Overview

C0000 is most commonly documented on GM/Saturn platforms as a steering-related module setting a fault because the vehicle speed message (from PCM/ECM/TCM via serial data) is missing/invalid; typical root causes are loss of speed message on the network, wiring/connector faults at the steering module, or faults in the originating module/speed source.

Common Symptoms

• Intermittent or reduced power steering assist (heavy steering, especially at low speed/parking)
• Steering-related warning message or indicator (varies by platform; may include service power steering or service 4-wheel steer)
• Rear wheel steering disabled or rear wheels returning to center (if equipped)
• Other communication or vehicle speed related DTCs stored in modules that source or consume the vehicle speed message
• Cruise control or speedometer anomalies may be present if the underlying speed signal source is affected (vehicle-dependent)

Most Common Causes

Diagnostic Steps

1. Record freeze frame/module context: identify which module set C0000 (power steering/PSCM, rear wheel steering module, ABS/EBCM, etc.) and capture all stored DTCs from all modules (not only the engine controller).
   Expected: C0000 appears in a steering-related module; additional vehicle-speed or communication DTCs (U-codes or speed-signal codes) may be present in source or network modules.
   Interpretation: If other vehicle speed or communication DTCs are present, prioritize diagnosing the upstream speed message source or network fault first; C0000 may be a downstream symptom.
2. Verify whether the steering module is receiving a valid vehicle speed parameter on the scan tool data list (PSCM/EPS or rear wheel steering module live data). Compare against PCM/ECM/TCM displayed vehicle speed at the same time.
   Expected: Either the steering module shows 0 or implausible speed while the PCM shows correct speed, or both show implausible/erratic speed.
   Interpretation: If PCM speed is correct but steering module speed is missing/incorrect, suspect network/message delivery or steering module connector/wiring. If both are incorrect, suspect the speed source (VSS/wheel-speed inputs) or the module that generates the speed value.
3. Check for related DTCs in the module that originates the vehicle speed message on that platform (often PCM/ECM/TCM, sometimes ABS/EBCM depending on architecture).
   Expected: Presence of codes related to vehicle speed sensor, wheel speed sensors, or network communications.
   Interpretation: Upstream DTCs increase the likelihood that C0000 is a secondary consequence; resolve upstream faults and re-test.
4. Perform a targeted visual and physical inspection of wiring/connectors at the steering control module (PSCM/EPS) and/or rear wheel steering module: look for water intrusion, corrosion/green terminals, loose terminal tension, chafing, pin push-out, and damaged grounds/power feeds.
   Expected: Evidence of poor connection, damaged insulation, corrosion, or intermittent contact; movement of harness may reproduce symptom.
   Interpretation: OEM-style diagnostic aids highlight poor connections/opens/shorts as common; repair connector/wiring defects before considering module replacement.
5. If the platform uses CAN/Class 2/GMLAN: check network health (bus voltages, resistance with power off, and scan tool network diagnostics). Isolate by unplugging suspect modules only per service procedures to avoid creating new faults.
   Expected: Abnormal bus resistance or voltages, multiple modules dropping offline, or intermittent communication errors.
   Interpretation: Network faults can block the speed message; correct bus wiring/termination or power/ground issues to the offending module(s).
6. If no wiring/network issues are found and the speed message source is confirmed valid, follow OEM test procedure for the steering module (PSCM/EPS or rear wheel steering module): verify power, ground, and communication pins under load; then consider module fault or calibration needs.
   Expected: Power/ground and network pins are correct but module still shows missing/invalid speed or sets C0000 immediately.
   Interpretation: With inputs confirmed good, module internal failure or required programming/calibration becomes more likely; replace/program per OEM procedures.
7. After repair, clear codes and perform a validation road test covering the conditions that set the code (low-speed steering maneuvers; steady cruise; if equipped, rear wheel steering mode checks). Re-scan all modules.
   Expected: C0000 does not return and steering assist/rear steer operation is normal across conditions.
   Interpretation: If C0000 returns, re-check for intermittents (connector tension, harness rub points) and re-evaluate upstream speed message integrity.

Repair Solutions

Frequently Asked Questions