Foxbody Mustang EEC-IV Error Codes
If there is an issue with your Foxbody Mustang (engine related), a good place to start is to check if the EEC-IV computer has registered any error codes. There are two ways to do so:
- Code scanner: You can buy a code scanner from almost any auto parts store, just verify that it can indeed read the error codes from Foxbody Mustangs. Plugin the code scanner to VIP/DLC connector harness in the engine bay (right-hand, driver side for 86-93) and read out any error codes, if there are any.
- Test light: For the procedure on how to pull the error codes from a Foxbody Mustang EEc-IV equipped car, please refer to: DIY KOEO/KOER/Cylinder Balance Self-Test Procedure
- A text (printer friendly) version of the EEC-IV codes are available here: Foxbody EEC-IV Error Codes (Printable)
Legend: O = Ignition On (accessory), R = Engine Running, C = Continuous Memory
| Code | Test Condition | Cause |
|---|---|---|
| 11 | O,R,C | System OK, testing complete |
| 12 | R | Idle speed control out of specified range |
| 13 | O,R,C | Normal idle not within specified range |
| 14 | O,C | Ignition profile pickup erratic |
| 15 | O | ROM test failure |
| 15 | C | Power interrupt to computer memory |
| 16 | R | Erratic idle, oxygen sensor out of range or throttle not closing |
| 17 | R | Curb idle out of specified range |
| 18 | R | SPOUT circuit open |
| 19 | O | No power to processor |
| 19 | R | Erratic idle speed or signal |
| 21 | O,R | Coolant temperature out of specified range |
| 21 | O,R,C | Coolant temperature sensor out of specified range |
| 22 | O,R,C | MAP sensor out of specified range |
| 23 | O,R,C | Throttle position signal out of specified range |
| 24 | O,R | Air charge temperature low |
| 25 | O,R | Mass Air Flow sensor or circuit |
| 27 | C | Vehicle Speed Sensor or circuit |
| 28 | 0,R | Vane air temperature sensor or circuit |
| 29 | C | No continuity In Vehicle Speed Sensor circuit |
| 31 | O,R,C | Canister or EGR valve control system |
| 32 | O,R,C | Canister or EGR valve control system |
| 33 | R,C | Canister or EGR valve not operating properly |
| 34 | O,R,C | EVP voltage above closed unit |
| 35 | O,R,C | EGR pressure feedback, regulator circuit |
| 38 | C | Idle control circuit |
| 39 | C | Automatic overdrive circuit |
| 41 | C | Oxygen sensor signal |
| 41 | R | Lean fuel mixture |
| 42 | R,C | Fuel mixture rich |
| 43 | C | Lean fuel mixture at wide open throttle - |
| 43 | R | Engine too warm for test |
| 44 | R | Air management system inoperative |
| 45 | R | Thermactor air diverler circuit |
| 46 | R | Thermactor air bypass circuit |
| 47 | R | Low flow of unmetered air at idle |
| 48 | R | High flow of unmetered air at idle |
| 49 | C | SPOUT signal defaulted to 1 0-degrees |
| 51 | O,C | Coolant temperature sensor out of specified range |
| 52 | O,R | Power steering pressure switch out of specified range |
| 53 | O,C | Throttle Position Sensor input out of specified range |
| 54 | O,C | Vane air flow sensor or air charge temperature sensor |
| 55 | R | Charging system under specified voltage (1984 through 1988) |
| 55 | R | Open ignition key power circuit (1984 through 1988) |
| 56 | O,R,C | Mass Air Flow sensor or circuit |
| 57 | C | Transmission neutral pressure switch circuit |
| 58 | O | CFI - idle control circuit; EFI - vane air flow circuit |
| 58 | R | Idle speed control motor or circuit |
| 58 | C | Vane air temperature sensor or circuit |
| 59 | O,C | Transmission throttle pressure switch circuit |
| 61 | O,C | Coolant temperature switch out of specified range |
| 62 | 0 | Transmission circuit fault |
| 63 | O,C | Throttle Position Sensor or circuit |
| 64 | O,C | Air Charge Temperature (ACT) sensor |
| 65 | C | Fuel control system not switching to closed loop |
| 66 | O,C | No Mass Air Flow sensor signal |
| 67 | O,R,C | Neutral drive switch or circuit |
| 67 | C | Air conditioner clutch switch circuit |
| 69 | O,C | Vehicle Speed Sensor or circuit |
| 72 | C | System power circuit, electrical interference |
| 72 | R | No Manifold Absolute Pressure or Mass Air Flow sensor signal fluctuation |
| 73 | O,R | Throttle Position Sensor or circuit 21 |
| 74 | R | Brake on/off ground circuit fault 21 |
| 75 | R | Brake on/off power circuit fault 22 |
| 76 | R | No vane airflow change |
| 77 | R | Throttle "goose" test not performed |
| 78 | C | Power circuit 1 |
| 79 | O | Air conditioner clutch circuit |
| 81 | O | Thermactor air circuit |
| 82 | O | Thermactor air circuit, integrated controller circuit |
| 83 | O | EGR control circuit (four-cylinder models oeM |
| 83 | O | Cooling fan circuit (V6 models only) |
| 83 | O,C | Low speed fuel pump relay (1984 through 1988 models) |
| 83 | O,C | EGR solenoid or circuit (1989 and later models) |
| 84 | O,R | EGR control circuit |
| 85 | O,R | Canister purge circuit or transmission shift control circuit |
| 85 | C | Excessive fuel pressure or flow |
| 85 | C | Canister purge circuit |
| 86 | C | Low fuel pressure or flow |
| 87 | O,R,C | Fuel pump circuit D2 |
| 88 | O | Integrated controller |
| 89 | O | Lock-up solenoid |
| 91 | R,C | Oxygen sensor problem, fuel pressure out of specified range or injectors out of balance |
| 92 | R | Fuel mixture rich, fuel pressure high |
| 93 | O | Throttle Position Sensor or circuit D |
| 94 | R | Secondary air system inoperative |
| 95 | O,C | Fuel pump circuit problem |
| 95 | R | Thermactor air diverter circuit |
| 96 | O,C | Fuel pump circuit |
| 96 | R | Thermactor air bypass circuit |
| 98 | R | Repeat test sequence |
| 99 | R | Repeat test sequence |
| 99 | R | System has not learned to control idle speed |
| 111 | O,R,C | System Pass |
| 112 | O,R,C | Air Charge Temp (Ad) Sensor circuit below minimum voLtagE/ 254 F |
| 113 | O,C | Air Charge Temp (ACT) Sensor circuit above maximum voltagE/ -40 F |
| 114 | O,R | Air Charge Temp (ACT) out of self test range |
| 116 | O,R | Coolant Temp (ECT) out of self test range |
| 117 | O,R | Coolant Temp (EdT) Sensor circuit below minimum voltage/ 254 F |
| 118 | O,C | Coolant Temp (EdT) Sensor circuit above maximum voitage/ -40 F |
| 121 | O,C | Closed Throttle Voitage higher or lower than expected |
| 122 | O,R,C | Throttle Position (TP) Sensor circuit below minimum voltage |
| 123 | O,C | Throttle Position (TP) Sensor circuit above maximum voltage |
| 124 | O,C | Throttle Position (TP) Sensor voltage higher than expected |
| 125 | C | Throttle Position fTP) Sensor voltage lower than expected |
| 126 | C | BP Sensor higher or lower than expected |
| 129 | O,R,C | Insufficient Mass Air Flow (MAE) change during Dynamic Response Test |
| 144 | C | No Oxygen Sensor (HEGO) Switches detected |
| 157 | C | Mass Air Flow (MAE) Sensor circuit below minimum voltage |
| 158 | O,C | Mass Air Flow (MAE) Sensor circuit above maximum voltage |
| 159 | O,R | Mass Air Flow (MAE) Sensor out of self test range |
| 167 | R | Insufficient Throttle Position change during Dynamic Response Test |
| 171 | C | Fuel system at adaptive limits, Oxygen Sensor (HEGO) unable to switch |
| 172 | R,C | Lack of Oxygen Sensor (HEGO) Switches, indicates lean |
| 173 | R,C | Lack of Oxygen Sensor (HEGO) Switches, indicates rich |
| 179 | C | Fuel system at lean adaptive limit at part throttle, system rich |
| 181 | C | Fuel system at rich adaptive limit at part throttle, system lean |
| 182 | C | Fuel system at lean adaptive limit at idle, system rich |
| 183 | C | Fuel system at flch adaptive limit at idle, system lean |
| 184 | C | Mass Air Flow (MAE) higher than expectec |
| 185 | C | Mass Air Flow (MAE) lower than expected |
| 186 | C | Injector pulse width higher than expected |
| 187 | C | Injector pulse width lower than expected |
| 211 | C | Profile Ignition Pickup (PIP) circuit fault |
| 212 | C | Ignition module circuit failure - SPOUT circuit grounded |
| 213 | R | SPOUT circuit |
| 214 | C | Cylinder Identification (CID) circuit failure |
| 215 | C | EEC Processor detected Coil 1 primary circuit failure |
| 216 | C | EEC Processor detected Coil 2 primary circuit failure |
| 218 | C | Loss of ignition Diagnostic Monitor (1DM) signal-left side |
| 222 | C | Loss of Ignition Diagnostic Monitor (1DM) signal-right side |
| 223 | C | Loss of Dual Plug Inhibit (DPI) control |
| 224 | C | Erratic Ignition Diagnostic Monitor (1DM) input to processor |
| 225 | R | Knock riot sensed during Dynamic Response Test |
| 327 | O,R,C | EVP circuit below minimum voltage |
| 328 | O,R,C | EGR "closed valve" voltage lower than expected |
| 332 | R,C | Insufflcjent EGR flow detected |
| 334 | O,R,C | EGR closed valve voltage higher than expected |
| 337 | O,R,C | EVP circuit above maximum voltage |
| 341 | O | Octane Adjust Service Pin in use |
| 411 | R | Cannot control RPM during KOER low rpm check |
| 412 | R | Cannot control rpm during KOER high rpm check |
| 452 | C | Isufflcient input from Vehicle Speed Sensor (VSS) |
| 511 | O | EEC Processor Read Only Memory (ROM) test failure |
| 512 | C | EEC Processor Keep 4Jive Memory (KAM) test failure |
| 519 | O | Power Steering Pressure Switch (PSPS) circuit open |
| 521 | R | Power Steering Pressure Switch (PSPS) circuit did not change states |
| 522 | O | Vehicle not in PARK or NEUTRAL during KOEO |
| 528 | C | Clutch Switch Circuit failure |
| 536 | R,C | Brake On/Off (BOO) circuit failure I not actuated during KOER |
| 538 | R | IsuffIcient RPM change during KOER Dynamic Response Test |
| 539 | O | AC On/Defrost ON during KOEO |
| 542 | O,C | Fuel Pump secondary circuit failure |
| 543 | O,C | Fuel Pump secondary circuit failure |
| 556 | O,C | Fuel Pump Relay primary circuit failure |
| 558 | O | EGR Vacuum Regulator (EVR) circuit failure |
| 564 | 0 | ElectrOD FAN( EDF) circuit failure |
| 565 | O | Canister Purge (CANP) circuit failure |
| 566 | O | 3-4 Shift Solenoid circuit failure |
| 629 | O | Converter Clutch Control circuit failure |
| 998 | O,R | Hard Fault present |
A text and printable version of the EEC-IV code list is available here