Navigating the complexities of vehicle diagnostics can be daunting, especially when dealing with older systems. For owners and enthusiasts of classic Ford vehicles, understanding OBD1 (On-Board Diagnostics I) codes is essential for effective troubleshooting and maintenance. This guide provides a comprehensive breakdown of Ford OBD1 diagnostic trouble codes, empowering you to understand your vehicle’s signals and address issues efficiently.
Before the standardized OBD2 system became mandatory in the mid-1990s, manufacturers like Ford utilized OBD1 systems. These earlier systems, while less standardized, still offer valuable insights into your vehicle’s health. This article will delve into the meaning of Ford OBD1 codes, helping you diagnose problems in your cherished Ford classic.
What are Ford OBD1 Codes?
Ford OBD1 codes are diagnostic trouble codes generated by the vehicle’s computer system when it detects a malfunction. Unlike the alphanumeric codes of OBD2, OBD1 codes are typically two-digit numbers. These codes are accessed through a specific diagnostic procedure, often involving counting flashes of the check engine light or using a scan tool compatible with OBD1 systems.
Understanding these codes is the first step in diagnosing a range of issues, from engine performance problems to sensor malfunctions. While OBD1 systems are less sophisticated than their modern counterparts, they are still invaluable for pinpointing the area of the vehicle requiring attention.
Ford OBD1 Trouble Codes Explained
The following table provides a detailed list of Ford OBD1 diagnostic trouble codes for fuel-injected systems. Please note that this list is a guide and should be used in conjunction with your vehicle’s repair manual for accurate diagnosis. Always consult a professional mechanic if you are unsure about any diagnostic or repair procedure.
| Code | Fuel Delivery Type | Description | OBD2 Equivalent (Approximate) |
|---|---|---|---|
| 11 | Injected | System Pass | N/A – System OK |
| 12 | Injected | Unable to control RPM during Self-Test high RPM check | P0507 – Idle Air Control System RPM Higher Than Expected |
| 13 | Injected | Unable to control RPM during Self-Test low RPM check | P0506 – Idle Air Control System RPM Lower Than Expected |
| 14 | Injected | Profile Ignition Pickup (PIP) circuit failure | P0320 – Ignition/Distributor Engine Speed Input Circuit Malfunction |
| 15 | Injected | 1. Electronic Engine Control (EEC / PCM) processor ROM test failure 2. Electronic Engine Control (EEC / PCM) processor Keep Alive Memory (KAM) test failed | P0605 – Internal Control Module Read Only Memory (ROM) Error / P0603 – Internal Control Module Keep Alive Memory (KAM) Error |
| 18 | Injected | 1. SPARK OUTPUT (SPOUT) circuit open 2. Ignition Diagnostic Monitor (IDM) circuit failure SPOUT circuit grounded | P0322 – Ignition/Distributor Engine Speed Input Circuit No Signal / P0321 – Ignition/Distributor Engine Speed Input Circuit Range/Performance |
| 19 | Injected | CID circuit failed | P0340 – Camshaft Position Sensor Circuit Malfunction |
| 21 | Injected | Engine Coolant Temperature (ECT) sensor out of Self-Test range | P0118 – Engine Coolant Temperature Circuit High Input / P0117 – Engine Coolant Temperature Circuit Low Input |
| 22 | Injected | Back Pressure (BP) sensor out of Self-Test range | P0404 – Exhaust Gas Recirculation Circuit Range/Performance |
| 23 | Injected | Throttle Position sensor (TPS) out of Self-Test range | P0123 – Throttle/Pedal Position Sensor/Switch A Circuit High Input / P0122 – Throttle/Pedal Position Sensor/Switch A Circuit Low Input |
| 24 | Injected | Air Charge Temperature sensor (IAT) out of Self-Test range | P0113 – Intake Air Temperature Circuit High Input / P0112 – Intake Air Temperature Circuit Low Input |
| 25 | Injected | Knock Sensor not sensed during Dynamic Response Test | P0325 – Knock Sensor 1 Circuit Malfunction (Bank 1 or Single Sensor) |
| 26 | Injected | Mass Air Flow sensor (MAF) out of Self-Test range | P0103 – Mass or Volume Air Flow Circuit High Input / P0102 – Mass or Volume Air Flow Circuit Low Input |
| 29 | Injected | Insufficient input from Vehicle Speed Sensor (VSS) | P0500 – Vehicle Speed Sensor A Malfunction |
| 31 | Injected | Pressure Feedback (PFE) circuit below minimum voltage | P0405 – Exhaust Gas Recirculation Sensor A Circuit Low |
| 32 | Injected | Pressure Feedback (PFE) circuit voltage low. | P0405 – Exhaust Gas Recirculation Sensor A Circuit Low |
| 33 | Injected | Exhaust Gas Recirculation (EGR) valve opening not detected | P0401 – Exhaust Gas Recirculation Flow Insufficient Detected |
| 34 | Injected | 1. Pressure Feedback (PFE) sensor voltage out of range 2. Exhaust back pressure high / Pressure Feedback (PFE) circuit voltage high | P0406 – Exhaust Gas Recirculation Sensor A Circuit High |
| 35 | Injected | Pressure Feedback (PFE) circuit above maximum voltage | P0406 – Exhaust Gas Recirculation Sensor A Circuit High |
| 41 | Injected | 1. Heated Oxygen Sensor (HO2S) circuit indicates system lean (rear HO2S). 2. No Heated Oxygen Sensor (HO2S) switching detected rear HO2S). | P0171 – System Too Lean (Bank 1) / P0131 – O2 Sensor Circuit Low Voltage (Bank 1, Sensor 2) |
| 42 | Injected | Heated Oxygen Sensor (HO2S) circuit indicates system rich (right HO2S). | P0172 – System Too Rich (Bank 1) / P0132 – O2 Sensor Circuit High Voltage (Bank 1, Sensor 2) |
| 45 | Injected | Coil 1 primary circuit failure | P0351 – Ignition Coil A Primary/Secondary Circuit Malfunction |
| 46 | Injected | Coil 2 primary circuit failure | P0352 – Ignition Coil B Primary/Secondary Circuit Malfunction |
| 48 | Injected | Coil 3 primary circuit failure | P0353 – Ignition Coil C Primary/Secondary Circuit Malfunction |
| 49 | Injected | Spark Output (SPOUT) signal defaulted to 10 degrees BTDC / SPOUT circuit open | P0322 – Ignition/Distributor Engine Speed Input Circuit No Signal |
| 51 | Injected | Engine Coolant Temperature sensor (CTS) indicate -40F / circuit open | P0118 – Engine Coolant Temperature Circuit High Input |
| 52 | Injected | 1. Power Steering Pressure Switch (PSPS) circuit is open 2. Power Steering Pressure Switch (PSPS) circuit did not change states | P0550 – Power Steering Pressure Sensor/Switch Circuit Malfunction |
| 53 | Injected | Throttle Position sensor (TPS) circuit above maximum voltage | P0123 – Throttle/Pedal Position Sensor/Switch A Circuit High Input |
| 54 | Injected | Air Charge Temperature sensor (IAT) indicates -40F / circuit open | P0113 – Intake Air Temperature Circuit High Input |
| 56 | Injected | Mass Air Flow (MAF) sensor input is greater than maximum voltage | P0103 – Mass or Volume Air Flow Circuit High Input |
| 59 | Injected | Low speed fuel pump circuit open (battery to ECA). | P0231 – Fuel Pump Secondary Circuit Low |
| 61 | Injected | Engine Coolant Temperature sensor (CTS) indicated 254F / circuit grounded | P0117 – Engine Coolant Temperature Circuit Low Input |
| 63 | Injected | Throttle Position sensor (TPS) circuit below minimum voltage | P0122 – Throttle/Pedal Position Sensor/Switch A Circuit Low Input |
| 64 | Injected | Air Charge Temperature sensor (IAT) indicated 254F / circuit grounded | P0112 – Intake Air Temperature Circuit Low Input |
| 66 | Injected | Mass Air Flow (MAF) sensor input is less than maximum voltage | P0102 – Mass or Volume Air Flow Circuit Low Input |
| 67 | Injected | Neutral Pressure Switch (NPS) circuit closed; A/C ON | P0850 – Park/Neutral Switch Input Circuit |
| 72 | Injected | Insufficient Mass Air Flow (MAF) output change during Dynamic Response Test | P0100 – Mass or Volume Air Flow Circuit Malfunction |
| 73 | Injected | Insufficient Throttle Position sensor (TPS) output change during Dynamic Response Test. | P0120 – Throttle/Pedal Position Sensor/Switch A Circuit Malfunction |
| 74 | Injected | Brake On/Off (BOO) circuit failure – not actuated during Self-Test | P0504 – Brake Switch A/B Correlation |
| 77 | Injected | Brief Wide Open Throttle (WOT) not sensed during Self-Test / Operator error | N/A – Test Procedure Error |
| 79 | Injected | A/C on / Defrost on during Self-Test | N/A – Test Condition Error |
| 81 | Injected | Idle Assist Solenoid (IAS) circuit failure | P0505 – Idle Air Control System Malfunction |
| 83 | Injected | Low speed primary fuel pump circuit failure | P0230 – Fuel Pump Primary Circuit Malfunction |
| 84 | Injected | Exhaust Gas Recirculation Vacuum Regulator (EVR) circuit failure | P0403 – Exhaust Gas Recirculation Circuit Malfunction |
| 85 | Injected | Canister Purge (CANP) circuit failure | P0443 – Evaporative Emission System Purge Control Valve Circuit Malfunction |
| 87 | Injected | Primary fuel pump circuit failure | P0230 – Fuel Pump Primary Circuit Malfunction |
| 88 | Injected | Electro-Drive Fan (EDF) circuit failure | P0480 – Fan Control Circuit 1 Malfunction |
| 91 | Injected | 1. Heated Oxygen Sensor (HO2S) indicates system lean (front – HO2S) 2. No Heated Oxygen Sensor (HO2S) switching detected (front – HO2S) | P0171 – System Too Lean (Bank 1) / P0130 – O2 Sensor Circuit Malfunction (Bank 1, Sensor 1) |
| 92 | Injected | Heated Oxygen Sensor (HO2S) sensor indicates system rich (front – HO2S) | P0172 – System Too Rich (Bank 1) / P0132 – O2 Sensor Circuit High Voltage (Bank 1, Sensor 1) |
| 95 | Injected | Fuel pump secondary circuit failure | P0231 – Fuel Pump Secondary Circuit Low |
| 96 | Injected | High speed fuel pump circuit open | P0232 – Fuel Pump Secondary Circuit High |
| 98 | Injected | Hard fault is present | N/A – General Fault Indication |
| No Codes | Injected | Unable to initiate Self-Test or unable to output Self- Test codes | N/A – Communication Error |
| Codes Not Listed | Injected | Service codes displayed are not applicable to the vehicle being tested | N/A – Incorrect Application |
Note: OBD2 equivalent codes are approximate and provided for general understanding. Always refer to Ford specific documentation for accurate diagnosis and repair.
This information, combined with careful observation, proper testing procedures, and the use of tools like a digital multimeter, will significantly aid in diagnosing and repairing your Ford vehicle effectively. Remember, this guide is not a substitute for official Ford service manuals or professional training. For in-depth diagnostics and complex repairs, always consult a qualified mechanic and refer to the factory service manual for your specific vehicle model and year.
[paragraph break]
