The EEC-IV equipped engines use an older diagnostic system to monitor and report engine related malfunctions. This system is known as On Board Diagnostics (OBD-I). The Diagnostic Trouble Codes (DTC’s) are two or three digit numbers and can be read through the use of a scan tool, an analog voltmeter, or with the Malfunction Indicator Light (MIL) [Check Engine or Service Engine Soon light].
Steps on how to test the EEC-IV / OBD-I vehicles can be found here at: Testing EEC-IV Equipped Engines
This page contains the 2-digits codes that you will get as a result of that test.
Differences in test mode noted as:
(O) = Key On Engine Off test
(R) = Key On Engine Running test
(M) = Memory code
| Code | Definitions |
|---|---|
| 111 | System checks OK |
| 112 | (O,M) Intake Air Temperature (IAT) sensor is/was low or grounded – IAT |
| 113 | (O,M) IAT sensor is/was high or open – IAT |
| 114 | (O,R) IAT sensor out of range – IAT |
| 116 | (O,R) Engine Coolant (ECT) sensor out of range – ECT |
| 117 | (O,M) ECT sensor is/was low or grounded – ECT |
| 118 | (O,M) ECT sensor is/was high or open – ECT |
| 121 | (O,R,M) Throttle Position (TP) sensor out of range – TPS |
| 122 | (O,M) TP low (possibly grounded or open circuit) – TPS |
| 123 | (O,M) TP is/was high or short to power – TPS |
| 124 | (M) TP voltage was higher than expected – Fuel control |
| 125 | (M) TP voltage was lower than expected – Fuel control |
| 126 | (O,R,M) MAP or BARO sensor out of range – “>MAP |
| 128 | (M) MAP vacuum has not been changing – check vacuum lines – “>MAP |
| 129 | (R) No MAP or Mass Air Flow sensor change during “goose” test – MAP MAF |
| 136 | (R) Oxygen sensor not switching/system lean Left or Front HO2S – Fuel control |
| 137 | (R) Oxygen sensor not switching/system rich Left or Front HO2S – Fuel control |
| 138 | (R) Fault in Cold Start Injector circuit – Fuel control |
| 139 | (M) Oxygen sensor not switching Left or Front HO2S – Fuel control |
| 144 | (M) Oxygen sensor not switching Single, Right or Rear HO2S – Fuel control |
| 157 | (R,M) Mass Air Flow signal is/was low or grounded – MAF |
| 158 | (O,R,M) MAF sensor is/was high or short to power – MAF |
| 159 | (O,R) MAF sensor is/was out of range – MAF |
| 167 | (R) No Throttle Position sensor change in “goose” test (must get at least 25% rotation) – TPS |
| 171 | (M) Oxygen sensor not switching – system was at adaptive limits – Single, Right or Rear HO2S – Fuel control |
| 172 | (R,M) Oxygen sensor not switching – system is or was lean – Single, Right or Rear HO2S – Fuel control |
| 173 | (R,M) Oxygen sensor not switching – system is or was rich – Single, Right or Rear HO2S – Fuel control |
| 174 | (M) Oxygen sensor was slow in switching Single, Right or Rear HO2S – Fuel control |
| 175 | (M) Oxygen sensor not switching – system was at adaptive limits – Left or Front HO2S – Fuel control |
| 176 | (M) Oxygen sensor not switching – system is or was lean Left or Front HO2S – Fuel control |
| 177 | (M) Oxygen sensor not switching – system was rich Left or Front HO2S – Fuel control |
| 178 | (M) Oxygen sensor was slow in switching Left or Front HO2S – Fuel control |
| 179 | (M) Fuel system was rich at part throttle Single, Right or Rear HO2S – Fuel control |
| 181 | (M) Fuel system was lean at part throttle Single, Right or Rear HO2S – Fuel control |
| 182 | (M) Fuel system was rich at idle Single, Right or Rear HO2S – Fuel control |
| 183 | (M) Fuel system was lean at idle Single, Right or Rear HO2S – Fuel control |
| 184 | (M) Mass Air (MAF) output higher than expected – Fuel control |
| 185 | (M) Mass Air (MAF) output lower than expected – Fuel control |
| 186 | (M) Injector pulse width longer than expected or Mass Air Flow (MAF) lower than expected – Fuel control |
| 187 | Injector pulse width shorter than expected or Mass Air Flow (MAF) higher than expected – Fuel control |
| 188 | (M) Fuel system was rich at part throttle – Left or Front HO2S – Fuel control |
| 189 | (M) Fuel system was lean at part throttle – Left or Front HO2S – Fuel control |
| 191 | (M) Fuel system was rich at idle – Left or Front HO2S – Fuel control |
| 192 | (M) Fuel system was lean at idle – Left or Front HO2S – Fuel control |
| 193 | Failure in Flexible Fuel (FF) sensor circuit – Fuel control |
| 194 | (M) Perform cylinder balance test to check for inoperative injectors |
| 195 | (M) Perform cylinder balance test to check for inoperative injectors |
| 211 | (M) Ignition PIP signal was erratic or missing – Ignition Systems |
| 212 | (M) Ignition TACH signal was erratic (module/wiring) or SPOUT circuit fault – Ignition Systems |
| 213 | (R) Ignition SPOUT or SAW circuit open or shorted – Ignition Systems |
| 214 | (M) Error in Cylinder ID (CID) circuit or signal – Ignition Systems |
| 215 | (M) Primary circuit failure – ignition coil 1 – Ignition Systems |
| 216 | (M) Primary circuit failure – ignition coil 2 – Ignition Systems |
| 217 | (M) Primary circuit failure – ignition coil 3 – Ignition Systems |
| 218 | (M) IDM signal open or high or left coil pack failure – Ignition Systems |
| 219 | (M) SPOUT circuit failure, timing defaulted to 10 degrees – follow code 213 diagnosis |
| 222 | (M) IDM open or high or right coil pack failure – Ignition Systems |
| 223 | (M) Dual Plug (DPI), SPOUT or IDM circuit fault – Ignition Systems |
| 224 | (M) Failure in ignition coil primary circuit – Ignition Systems |
| 225 | (R) Knock sensor not tested (ignore if not pinging) – KS |
| 226 | (O) Ignition Diagnostic Monitor (IDM) signal fault – Ignition Systems |
| 232 | (M) EI primary coil circuit failure – Ignition Systems |
| 238 | (M) EI primary circuit failure – ignition coil 4 – Ignition Systems |
| 311 | (R) AIR system not working – Single, Right or Rear HO2S – Air Injection |
| 312 | (R) AIR not diverting – Air Injection |
| 313 | (R) AIR not bypassing – Air Injection |
| 314 | (R) AIR inoperative, Left or Front HO2S – Air Injection |
| 326 | (R,M) Pressure Feedback EGR shows low pressure EGR not seating or not seating intermittently – PFE |
| 327 | (O,R,M) EGR feedback signal is/was low – EVR or PFE |
| 328 | (O,R,M) EGR Valve Position (EVP) is/was low – EVR |
| 332 | (R,M) EGR did not open/respond during test or if memory code, did not open intermittantly – EVR or PFE |
| 334 | (O,R,M) EVP sensor is/was high – EVR |
| 335 | (O) EGR feedback signal is/was out of range – EVR or PFE |
| 336 | (O,R,M) PFE sensor signal is/was was high – “>PFE |
| 337 | (O,R,M) EGR feedback signal is/was was high – EVR |
| 338 | (M) Cooling system did not heat up (check cooling system / thermostat operation) |
| 339 | (M) Cooling system overheated (check cooling system / thermostat operation) |
| 341 | (O) Octane jumper installed (information only code to notify you if it is installed) |
| 411 | (R) Idle speed system not controlling idle properly (generally idle too high) – ISC |
| 412 | (R) Idle speed system not controlling idle properly (generally idle too low) – ISC |
| 452 | (M) Vehicle Speed Sensor (VSS) problem |
| 511 | (O) No power to PCM pin 1 or bad PCM (processor) |
| 512 | (M) Memory power (PCM pin 1) was interrupted – Was battery disconnected ? |
| 513 | (O) Replace processor (PCM) (internal failure) |
| 519 | (O) PSP switch/circuit open – PSP |
| 521 | (R) Wheel not turned during test or PSP problem – PSP |
| 522 | (O) Park/Neutral Position (PNP) or Clutch Pedal Position (CPP) circuit fault – PNP |
| transmission MLP sensor out of range in park – Transmissions | |
| 524 | Problem in low speed fuel pump circuit – Power / Fuel Pump Circuits |
| 525 | (O,M) Park/Neutral Position (PNP) or Clutch Pedal Position (CPP) circuit fault – PNP |
| 528 | (M) System shows voltage at pin 10 (is A/C on ?) or pin 30 (PNP, CPP switch) – PNP |
| 529 | (M) Data Communications Link to processor failure |
| Service any EEC codes, erase memory and retest. If code is still present refer to instrument cluster diagnosis manual. | |
| 533 | (M) Data Communications Link to instrument cluster failure – see 529 |
| 536 | (O,R,M) Brake On Off open or shorted to ground – BOO |
| 538 | (R) System did not receive “goose” test – TESTS |
| 539 | (O) System shows voltage at PCM pin 10. Is A/C on ? |
| 542 | (O,M) Fuel pump open, bad ground or always on – – Power / Fuel Pump Circuits |
| 543 | (O) Fuel pump monitor circuit shows no power – Power / Fuel Pump Circuits |
| (M) (Service 556 code first if present) Fuel pump relay or battery power feed was open – Power / Fuel Pump Circuits | |
| 551 | Problem in Intake Manifold Runner Control (IMRC) solenoid/circuit – Solenoids |
| 552 | (O) AIRB solenoid/circuit failure – Solenoids |
| 553 | (O) AIRD solenoid/circuit failure – Solenoids |
| 554 | (O) Fuel Press Regulator Control solenoid/circuit fault – Power / Fuel Pump Circuits |
| 556 | (O,M) Fuel pump relay primary circuit fault – Power / Fuel Pump Circuits |
| 557 | (O,M) Low speed pump relay primary circuit fault – Power / Fuel Pump Circuits |
| 558 | (O) EGR vacuum regulator solenoid/circuit failure – EVR or PFE or Solenoids |
| 559 | (O) A/C relay primary circuit fault – A/C and Fan Circuits |
| 563 | (O) High Fan Control (HFC) circuit failure – A/C and Fan Circuits |
| 564 | (O) Fan Control (FC) circuit failure – A/C and Fan Circuits |
| 565 | (O) Canister Purge 1 solenoid/circuit failure – Solenoids |
| 566 | (O) transmission 3/4 shift solenoid/circuit – Transmissions |
| 569 | (O) Canister Purge 2 solenoid/circuit failure – Solenoids |
| 578 | (M) A/C pressure sensor VREF short to ground – A/C and Fan Circuits |
| 579 | (M) ACP sensor did not change with A/C on – A/C and Fan Circuits |
| 581 | (M) Cooling fan current was excessive – A/C and Fan Circuits |
| 582 | (O) Open cooling fan circuit – A/C and Fan Circuits |
| 583 | (M) Fuel pump current was excessive – Power / Fuel Pump Circuits |
| 584 | (M) Open power ground circuit – Power / Fuel Pump Circuits |
| 585 | (M) A/C clutch current was excessive – A/C and Fan Circuits |
| 586 | (M) Open circuit in A/C clutch – A/C and Fan Circuits |
| 587 | (O, M) Communication problem between PCM and Variable Control Relay Module (VCRM) – Power / Fuel Pump Circuits |
| 617 | (M) Transmission shift failure (1/2 shift) – Transmissions |
| 618 | (M) Transmission shift failure (2/3 shift) – Transmissions |
| 619 | (M) Transmission shift failure (3/4 shift) – Transmissions |
| 621 | (O) Solenoid/circuit failure – shift solenoid 1 – Transmissions |
| 622 | (O) Solenoid/circuit failure – shift solenoid 2 – Transmissions |
| 624 | (O,M) Solenoid/circuit failure -Electronic Pressure Control (EPC) current is high – Transmissions |
| 625 | (O,M) Solenoid/circuit failure – Electronic Pressure Control (EPC) current is low – Transmissions |
| 626 | (O) Transmission Coast Clutch (CCS) Solenoid/circuit fault – Transmissions |
| 627 | (O) Torque Converter Clutch circuit fault – Transmissions |
| 628 | (M) Excessive converter clutch slippage – Transmissions |
| 629 | (O,M) Torque Converter Clutch circuit fault – Transmissions |
| 631 | (O) Overdrive Cancel Light circuit problem – Transmissions |
| 632 | (R) E4OD – Transmission Control Switch (TCS) should be cycled once between engine ID and Goose test |
| 633 | (O) 4x4L switch should be in 4×2 or 4×4 high for the test |
| 634 | (O,M) Park/Neutral Position (PNP) or Clutch Pedal Position (CPP) circuit fault |
| Electronic shift transmission – Manual Lever Position (MLP) sensor out of range in PARK – Transmissions | |
| 636 | (O,R) Transmission Oil Temperature (TOT) sensor out of range – Transmissions |
| 637 | (O,M) TOT sensor is/was high or open – Transmissions |
| 638 | (O,M) TOT sensor is/was low or grounded – Transmissions |
| 639 | (R,M) Transmission Speed sensor (TSS) circuit fault – Transmissions |
| 641 | (O) Transmission solenoid/circuit failure Shift Solenoid 3 – Transmissions |
| 643 | (O)(M) Torque Converter Clutch (TCC) circuit – Transmissions |
| 645 | (M) Transmission 1st gear failure – Transmissions |
| 646 | (M) Transmission 2nd gear failure – Transmissions |
| 647 | (M) Transmission 3rd gear failure – Transmissions |
| 648 | (M) Transmission 4th gear failure – Transmissions |
| 649 | (M) Transmission EPC system failure – Transmissions |
| 651 | (M) Transmission EPC solenoid/circuit fault – Transmissions |
| 652 | (O) Torque Converter Clutch (TCC) circuit fault – Transmissions |
| 654 | (O) Transmission selector not in PARK – Transmissions |
| 656 | (M) Torque Converter Clutch (TCC) slip – Transmissions |
| 657 | (M) Transmission temperature was excessive – Transmissions |
| 998 | (R) Did not pass Key On Engine Off test yet (Get 111 in KOEO first) |
| (O) Transmission Electronic Pressure Control (EPC) solenoid/circuit fault – Transmissions | |
| Code | Definitions: |
| ACT | Air Charge Temperature Sensor |
| BP | See MAP |
| EEC | Electronic Engine Control System |
| ECT | Engine Coolant Temperature Sensor |
| EGR | Exhaust Gas Recirculation Valve |
| EVP | EGR Valve Position Sensor |
| HEGO | Heated Exhaust Gas Oxygen Sensor |
| KOEO | Key On Engine Off |
| KOER | Key On Engine Running |
| MAF | Mass Air Flow Sensor |
| MAP | Manifold Absolute Pressure Sensor |
| MLP | Manual Lever Position |
| PCM | Powertrain Control Module |
| SPOUT | Distributor Jumper to Allow Initial Timing |
| TP | Throttle Position Sensor |
About The Author
Jim Oaks is the founder of The Ranger Station (TRS), one of the longest-running Ford Ranger enthusiast communities on the web. He has spent over three decades owning, modifying, repairing, and driving Ford Rangers on the street, trail, and overlanding routes.
Since launching TheRangerStation.com in 1999, Jim has documented thousands of real-world Ranger builds, technical repairs, drivetrain swaps, suspension modifications, and off-road adventures. TRS has been heavily referenced by enthusiasts, mechanics, and off-road builders looking for practical, experience-based information.