Kelley's Works in Progress

OBD-II Diagnostic Trouble Codes

Here's a reference for OBD-II Diagnostic Trouble Codes (DTC's.) The OBD-II specification applies to 1996 and up Jeep vehicles. And OBD-III is planned, but hasn't happened yet.

The "key cycling" trick (cf. OBD-I) doesn't usually work for OBD-II vehicles, so you'll need a code scanner of some variety. Fortunately, the abound in the automotive aftermarket, and some are priced within reach of the hobbyist - at under $200. Some searching will also turn up interfaces for handheld computers and laptop computers to OBD-II systems - which would allow you to use a device you may already own, and make for a little more powerful scan tool as well.

Please note that there are, in fact, several codes for each fault. Some code scanners will flash the code on the Check Engine Light (CEL,) and some will also display the regular Diagnostic Trouble Code (DTC.) Some will display hexadecimal codes, so use that column if the code you get doesn't make sense.

Last, there are the "P-codes" that are listed - those are the standard OBD-II codes, and will be used by high-end scanners as well. If you get a five-digit code that starts with the letter "P," use that column.

Also, some codes will cause a "hard fault" - which will light the CEL on the gage cluster. Some are "soft faults," which will not light the CEL. "Hard" codes will have a RED background, and "soft" codes will be in GREEN.

These codes are taken from the 1997 FSM - but they should not have changed over the years. OBD is an industrywide standard - and the only changes made are additions over time.

Where possible, I've tried to combine related codes (either opposites, or multiple components of the same system) with the same DTC for simplicity. The codes are arranged in DTC order, if there are enough requests I may create additional tables in order by Hex code and by OBD-II code - but having them listed by DTC will be more compleat and probably easier for the hobbyist.

Here's the codes:
DTC Hex Code OBD-II Code Meaning Explanation
11 28 --- No Crank Reference Signal at PCM No crankshaft position reference signal detected during engine cranking
11 9D P1391 Intermittent loss of CMP or CKP signal Inconsistent signal provided Crankshaft Position Sensor (CKP) or Camshaft Postion Sensor (CMP)
11 BA P1398 Misfire Adaptive Numerator at limit Crankshaft Position Sensor target windows have too much variation
12 --- --- Battery Disconnect Direct Battery Input to PCM disconnected in the last 50 ON/OFF cycles
13 27 P1297 No Change in MAP from "Start" to "Run" No difference recognised in engine MAP reading and the barometric/atmospheric pressure read at startup
14 24/25 P0107/P0108 MAP sensor Voltage too Low/High MAP sensor input voltage out of limits
14 87 P1296 No 5 Volts to MAP sensor MAP sensor input voltage not present - correct open circuit
15 23 P0500 No Vehicle Speed Sensor Signal No Vehicle Speed Sensor (VSS) Signal detected during "road load" conditions
17 21 --- Engine is "cold" too long Engine did not reach operating tempeature within acceptable limits
17 80 P0125 Closed Loop Temperature not reached Engine does not reach 20 degrees Fahrenheit withing 5 minutes with a VSS reading
21 66/67 P0133/P0135 Upstream HEGO sensor Slow Response/Heater Failure Upstream HEGO sensor response slower than minimum required switching frequency/Heating Element Failure
21 69 P0141 Downstream/Pre-catalyst HEGO Sensor Heater Failure Downstream/Pre-catalyst HEGO sensor heating element failure
21 3E P0132 Upstream HEGO sensor shorted to voltage HEGO sensor input voltage maintained above normal range
21 7E P0138 Catalyst HEGO Sensor shorted to voltage HEGO Sensor Input voltage maintained above the normal operating range
21 9B P0131 Upstream HEGO sensor shorted to Ground HEGO Sensor Supply voltage too low, tested after "cold" start cycle
21 9C P0137 Downstream/Pre-catalyst HEGO sensor shorted to Ground HEGO sensor voltage too low, tested after "cold" start
21 C0 P0133 Catalyst Monitor Slow HEGO 1/1 A slowly-switching HEGO sensor has been detected in Bank 1/1 during catalyst monitor test
22 1E/1F P0117/P0118 ECT Sensor Supply Voltage too Low/High Engine Coolant Temperature (ECT) Sensor supply Voltage out of limits
23 39/3A P0112/P0113 IAT Sensor Voltage too Low/High Intake Air Temperature (IAT) Sensor supply voltage out of limits
24 1A/1B P0122/P0123 TPS Voltage too Low/High Throttle Position Sensor (TPS) supple voltage out of limits
24 84 P0121 TPS does not agree with MAP TPS signal does not agree with MAP signal
25 19 P0505 IAC Circuits A "short" or "open" condition detected in one or more of the idle air control circuits
25 8A P0740 Target Idle Not Reached Actual Idle Speed does not equal Target Idle Speed
27 13/14/15/3D/45/46 P0203/P0202/P0201/P0204/P0205/P0206 Injector Control Circuit Failure Fuel Injector Driver #1/#2/#3/#4/#5/#6 does not respond properly to control signal
31 12 P0443 EVAP Purge Solenoid Circuit Evaporative Cannister Purge Control Solenoid Control circuit "open" or "short"
31 71 P0441 Evaporative Purge Flow Monitor Failure Insufficient or excessive vapour flow detected during evaporative emission system operation
32 0F --- Speed Control Solenoid Circuits An "open" or "short" circuit detected in the Speed Control Vacuum or Vent soenoid control circuits
33 10 --- Air Conditioning Clutch Relay Circuit An "open" or "short" circuit detected in the Air Conditioning Clutch Relay circuit
34 56/57 --- Speed Control Switch always High/Low Speed control switch input outside of limits
35 0E P1491 Radiator Fan Control Relay Circuit An "open" or "short" circuit detected in the Electric Radiator Fan Control Relay circuit
37 72 P1899 Park/Neutral Switch stuck in Park or Gear Incorrect input state reported by Park/Neutral switch (Automatic Transmission Only)
37 94 P0740 TCC, no RPM drop with Lockup Relationship between engine speed and vehicle speed indicates no Torque Converter Clutch (TCC) engagement
37 0C P0743 TCC Solenoid/Transmission Relay Circuit An "open" or "short" circuit detected in the torque converter part throttle unlock solenoid control circuit (3-speed Automatic RH transmission only)
41 0B --- Alternator Field not switching properly An "open" or "shorted" circuit found in the alternator field control circuit
42 0A --- ASD Relay Control Circuit An "open" or "short" circuit detected in the Auto Shut-Down Relay (ASD Relay) control circuit
42 2C --- No ASD Relay Output voltage at PCM An "open" condition detected in the Auto Shut-Down (ASD) Relay Control Circuit
42 65 --- Fuel Pump Relay Circuit An "open" or "short" circuit detected in the fuel pump relay control circuit
42 95/96 --- Fuel Level Sending Unit voltage too Low/High Fuel Level Sending Unit voltage out of limits
42 97 --- Fuel Level Unit no change with Miles Fuel Level signal does not change over time
43 6A P0300 Multiple Cylinder Misfire Misfire condition detected in multiple cylinders
43 6B/6C/6D/6E P0301 - P0304 Cylinder Misfire Misfire condition detected in cylinder #1/2/3/4
44 99/9A P1493/P1492 Ambient/Battery temperature sensor out of limit Battery Temperature Sensor Input voltage out of limits
46 06 --- Charging System Voltage High Battery Voltage Sense input above target charging voltage during engine operation
47 05 --- Charing System Voltage Low Battery Voltage Sense input below target charging voltage during engine operation. Also, no significant change detected in battery voltage during active test of Alternator Output circuit
49 AE/AF P0305/P0306 Cylinder Misfire Misfire condition detected in cylinder #5/#6
51 77 P0171 Fuel System Lean A "Lean" Air/Fuel Ratio (AFR) has been indicated by an abnormally "Rich" correction factor
52 76 P0172 Fuel System "Rich" A "Rich" AFR has been indicated by an abnormally "Lean" correction factor
53 02 P0601 Internal Controller Failure A Powertrain Control Module (PCM) internal failure has been detected
53 44 P0600 PCM Internal Fault/SPI Communications A Powertrain Control Module (PCM) communications fault has been detected
54 01 P0340 No Cam Signal at PCM No camshaft (SYNC) signal detected at Powertrain Control Module (PCM) during engine cranking
55 --- --- Display Finished Completion of DTC display on CEL/MIL
63 31 P1696 PCM Failure, EEPROM Write Denied An attempt by the Powertrain Control Module (PCM) to store date to an internal EEPROM was unsuccessful
77 52 --- Speed Control Relay, or Speed Control 12V Driver Circuit Malfunction detected with power feed to Speed Control Servos


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