What are ISO/SAE Reserved Codes?
ISO/SAE reserved diagnostic codes (such as P00C0 to P00FF) often indicate that a vehicle’s electronic systems do not comply with the communication standards set by the International Organization for Standardization (ISO) and SAE International, rather than pointing to a specific component failure.
About ISO and SAE Regulatory Bodies
ISO (International Organization for Standardization) and SAE (SAE International) are two organizations that establish technical standards for the automotive and aerospace industries. Through their collaboration, a set of mandatory guidelines for On-Board Diagnostics systems (OBD-II) has been established since late 1995.
These standards ensure reliable high-speed communication between onboard computers while minimizing conflicting messages and electromagnetic interference.
The Critical Role of CAN Bus
The CAN Bus (Controller Area Network) is the primary network through which the main computer (PCM) communicates with numerous onboard controllers (up to 70 in modern vehicles). When the PCM detects communication errors or non-compliance with ISO/SAE standards on this network, it may record fault codes and illuminate the malfunction indicator light.
Severity and Symptoms of ISO/SAE Reserved Codes
Since the severity of these codes can vary significantly, conducting thorough diagnostics is essential.
Possible Symptoms
- Multiple unpredictable driving symptoms
- No apparent symptoms (intermittent faults)
- Presence of other related fault codes
Potential Causes
- Damaged wiring or loose/corroded connectors
- Faulty electronic control units
- Control unit programming or software issues
- Power supply problems (weak battery, alternator)
Diagnostic Procedures
Diagnosing ISO/SAE reserved codes can be complex. Below are the recommended procedures:
- Prioritize checking and repairing all other fault codes first.
- Refer to Technical Service Bulletins (TSBs) applicable to your vehicle.
- Visually inspect the CAN Bus wiring and connectors for any damage, corrosion, or signs of rodent activity.
- Check the battery’s charge state and terminal connections. Voltage drops can trigger these codes.
- Use a professional-grade OBD-II scanner to read freeze frame data and clear codes. Test the vehicle to see if the fault recurs.
- Perform a “wiggle test” on wiring harnesses and connectors while the engine is running to identify intermittent issues.
Examples of ISO/SAE Reserved Codes
P00C0, P00C1, P00C2, P00C3, P00C4, P00C5, P00C6, P00C7, P00C8, P00C9, P00CA, P00CB, P00CC, P00CD, P00CE, P00CF, P00D0, P00D1, P00D2, P00D3, P00D4, P00D5, P00D6, P00D7, P00D8, P00D9, P00DA, P00DB, P00DC, P00DD, P00DE, P00DF, P00E0, P00E1, P00E2, P00E3, P00E4, P00E5, P00E6, P00E7, P00E8, P00E9, P00EA, P00EB, P00EC, P00ED, P00EE, P00EF, P00F0, P00F1, P00F2, P00F3, P00F4, P00F5, P00F6, P00F7, P00F8, P00F9, P00FA, P00FB, P00FC, P00FD, P00FE, P00FF.
Having trouble diagnosing your vehicle’s fault codes? To avoid the risk of damaging control units, consult a qualified mechanic equipped with appropriate diagnostic tools.