Decoding Your Jeep Grand Cherokee OBD2 Codes: A Comprehensive Guide

Navigating car troubles can be stressful, especially when the check engine light illuminates in your Jeep Grand Cherokee. Fortunately, modern vehicles like the Grand Cherokee are equipped with an On-Board Diagnostics system, or OBD, which can help pinpoint potential issues. This system generates codes that can be accessed and interpreted to understand what might be going wrong. This guide will walk you through understanding and retrieving OBD2 codes in your Jeep Grand Cherokee, empowering you with valuable information for diagnosis and repair.

Understanding OBD and Reading Codes on Your Jeep Grand Cherokee

The OBD system is essentially your car’s self-diagnostic tool. It monitors various systems within your vehicle, from the engine and transmission to emissions and more. When it detects a problem, it stores a Diagnostic Trouble Code (DTC) and often illuminates the check engine light. These codes are standardized, especially OBD2 codes which became mandatory in the United States in 1996, offering a consistent way to understand vehicle issues across different makes and models, including your Jeep Grand Cherokee.

Before diving into the codes themselves, it’s crucial to know how to retrieve them from your Jeep Grand Cherokee. There are a couple of methods, depending on the age of your vehicle.

The “Key Trick” for Retrieving OBD Codes

While modern OBD2 scanners provide the most user-friendly and detailed access to diagnostic information, Jeep Grand Cherokees, like many Chrysler vehicles, offer a built-in method to display basic OBD codes using the ignition key. This is often referred to as the “key trick.” It’s important to note that this method may display a limited set of codes compared to a dedicated scanner, but it can be a helpful starting point.

For Older (OBDI) Jeep Grand Cherokees

For older Jeep Grand Cherokee models, typically those manufactured before 1996 which utilize the OBDI system, the “key trick” involves a specific sequence of turning the ignition key:

Start with the ignition OFF.
Within five seconds, cycle the key ON, OFF, ON, OFF, ON. (Remember, “ON” is the position right before starting the engine, and “OFF” is not “LOCK”, but the position where the engine is off but accessories might still work).
Observe the “check engine” light. It will begin to flash.
Count the flashes. OBDI codes are typically two-digit codes. For example, a code 23 would be represented by two flashes, a pause, then three flashes, followed by a longer pause before the next code or the end sequence.
Code 55 indicates “End of Codes” and is a normal signal that the system has finished displaying all stored codes. If you see repeating “23 23” flashes, it’s likely just a single code 55 being displayed due to variations in blink spacing. Codes are generally not repeated.

For Newer (OBDII) Jeep Grand Cherokees

For newer Jeep Grand Cherokee models (1996 and onwards) equipped with OBDII, a slightly different “key trick” may work. This method often displays the codes directly on the digital odometer:

Insert the key into the ignition.
Push and hold down the odometer reset button.
Turn the key to the RUN position (again, just before starting the engine) while still holding the odometer reset button.
Release the odometer reset button.
The odometer display will cycle through various displays, including potentially “111111” to “999999”, and then might show the car’s serial number.
Finally, it should display any stored error codes, often prefixed with “P” (for Powertrain codes).
If this OBDII method doesn’t work, you can also try the OBDI method on some newer models as a fallback, though it’s less likely to be effective on true OBDII systems.

Important Note: The “key trick” methods are basic and may not work on all Jeep Grand Cherokee models, especially as systems become more sophisticated. For a reliable and comprehensive diagnostic reading, using an OBD2 scanner is always recommended. Scanners can provide more detailed codes, subcodes, and even live data from your vehicle’s sensors.

Jeep Grand Cherokee OBD Code Lists

Once you have retrieved the codes using the “key trick” or an OBD2 scanner, you’ll need to understand what they mean. Below are lists of common OBDI and OBDII codes relevant to Jeep vehicles, including the Grand Cherokee. Remember that while these lists are extensive, they may not be exhaustive, and the specific codes for your Jeep model year can vary. Always consult your Jeep Grand Cherokee’s repair manual or a professional mechanic for the most accurate diagnosis and repair information.

OBDI Codes for Jeep Grand Cherokee (Pre-1996 Models)

11: No ignition reference signal detected during cranking OR timing belt skipped one or more teeth; OR loss of either camshaft or crankshaft position sensor.
12: Battery or computer recently disconnected. (This code can be normal after battery service)
13: MAP sensor or vacuum line may not be working.
14: MAP sensor voltage below .16V or over 4.96V.
15: No speed/distance sensor signal.
16: Loss of battery voltage detected with engine running.
17: Engine stays cool too long (bad thermostat or coolant sensor?) OR 17 (1985 turbo only): knock sensor circuit.
21: Oxygen sensor signal doesn’t change (stays at 4.3-4.5V). Probably bad oxygen sensor.
22: Coolant sensor signal out of range – May have been disconnected to set timing.
23: Incoming air temperature sensor may be bad.
24: Throttle position sensor over 4.96V.
25: Automatic Idle Speed (AIS) motor driver circuit shorted or target idle not reached.
26: Peak injector circuit voltage has not been reached (need to check computer signals, voltage regulator, injectors).
27: Injector circuit isn’t switching when it’s told to (TBI) OR (MPI) injector circuit #1 not switching right OR (turbo) injector circuit #2 not switching right OR (all 1990-) injector output driver not responding – check computer, connections.
31: Bad evaporator purge solenoid circuit or driver.
32 (1984 only): power loss/limited lamp or circuit OR 32 EGR gases not working (1988): – check vacuum, valve OR 32 (1990-92): computer didn’t see change in air/fuel ratio when EGR activated – check valve, vacuum lines, and EGR electrical.
33: Air conditioning clutch relay circuit open or shorted (may be in the wide-open-throttle cutoff circuit or normal on early 80’s models if you don’t have air conditioning).
34 (1984-86): EGR solenoid circuit shorted or open OR 34 (1987-1991): speed control shorted or open.
35: Cooling fan relay circuit open or shorted OR 35: idle switch motor fault – check connections.
36 (turbo only): Wastegate control circuit open or shorted.
37: Shift indicator light failure, 5-speed OR part throttle lock/unlock solenoid driver circuit (87-89) OR solenoid coil circuit (85-87 Turbo only) OR Trans temperature sensor voltage low (1995 and on).
41: Alternator field control circuit open or shorted.
42: Automatic shutdown relay circuit open or shorted OR 42: Fuel pump relay control circuit OR 42: Fuel level unit – no change over miles OR 42: Z1 voltage missing when autoshutdown circuit energized (The Z1 voltage is the voltage of the circuits fed by the autoshutdown relay. This typically includes fuel pump and switched-battery feed to the ignition coil).
43: Peak primary coil current not achieved with max dwell time OR 43: Cylinder misfire OR 43: Problem in power module to logic module interface.
44: No FJ2 voltage present at logic board OR 44: Logic module self-diagnostics indicate problem OR 44: Battery temperature out of range.
45: Turbo boost limit exceeded (engine was shut down by logic module).
46: Battery voltage too high during charging or charging system voltage too low.
47: Battery voltage too low and alternator output too low.
51: Oxygen sensor stuck at lean position (this may be tripped by a bad MAP sensor system causing a rich condition. If you get hot rough idle and stalling, especially on deceleration, accompanied by flooded engine and difficulty restarting, that can be a bad MAP sensor causing the O2 sensor to try to compensate. If you get poor cold driveability, stumbling and bucking, and acceptable warm driving with poor gas mileage (a drop of 10 mpg or more), that is usually the O2 sensor. OR 51: Internal logic module fault (’84 turbo only).
52: Oxygen sensor stuck at rich position OR 52: Internal logic module fault (’84 turbo only).
53: Logic module internal problem.
54: No sync pickup signal during engine rotation (turbo only) OR 54: Internal logic module fault (’84 turbo only) – or camshaft sensor/distributor timing.
55: End of codes (Normal).
61: “Baro” sensor open or shorted.
62: EMR mileage cannot be stored in EEPROM OR PCM failure SRI mile not stored.
63: Controller cannot write to EEPROM.
64: Catalytic converter efficiency failure.
65: Power steering switch failure.
66: No CCD Message From TCM and/or No CCD Message From BCM.

OBDII Codes for Jeep Grand Cherokee (1996 and Newer Models)

OBDII codes are generally five characters long. They start with a letter indicating the system (P for Powertrain, B for Body, C for Chassis, U for Network), followed by a digit indicating whether it’s a generic (0) or manufacturer-specific (1) code, and then three more digits specifying the fault. Below is a list of common OBDII codes you might encounter with your Jeep Grand Cherokee. This is not an exhaustive list, and for definitive diagnosis, always consult a professional or a dedicated OBD2 resource.

P0030, P0036, P0130, P0136, P0142: O2 Sensor Circuit Malfunction (various banks and sensors).
P0106, P0107, P0108: MAP (Manifold Absolute Pressure) Sensor Voltage Range/Performance Issues.
P0112, P0113: Intake Air Temperature Sensor Circuit Low/High Input.
P0117, P0118: Engine Coolant Temperature Sensor Circuit Low/High Input.
P0121, P0122, P0123: Throttle Position Sensor (TPS) Circuit Range/Performance Issues.
P0125: Insufficient Coolant Temperature for Closed Loop Fuel Control.
P0131, P0132, P0137, P0138: O2 Sensor Circuit Low/High Voltage (various banks and sensors).
P0133, P0139: O2 Sensor Circuit Slow Response (various banks and sensors).
P0134, P0140: O2 Sensor Circuit No Activity Detected (various banks and sensors).
P0141, P0147: O2 Sensor Heater Circuit Malfunction (various banks and sensors).
P0151, P0152, P0157, P0158: O2 Sensor Circuit Low/High Voltage (Bank 2, various sensors).
P0153, P0159: O2 Sensor Circuit Slow Response (Bank 2, various sensors).
P0154, P0160: O2 Sensor Circuit No Activity Detected (Bank 2, various sensors).
P0161, P0167: O2 Sensor Heater Circuit Malfunction (Bank 2, various sensors).
P0171, P0174: System Too Lean (Bank 1 & Bank 2).
P0172, P0175: System Too Rich (Bank 1 & Bank 2).
P0201 – P0208: Injector Circuit Malfunction (Cylinders 1-8).
P0300: Random/Multiple Cylinder Misfire Detected.
P0301 – P0308: Cylinder Misfire Detected (Cylinders 1-8).
P0320: Crankshaft Position Sensor Circuit Malfunction.
P0325, P0330: Knock Sensor Circuit Malfunction (Sensor 1 & Sensor 2).
P0340: Camshaft Position Sensor Circuit Malfunction.
P0401: EGR (Exhaust Gas Recirculation) Flow Insufficient Detected.
P0403: EGR Solenoid Control Circuit Malfunction.
P0404, P0405, P0406: EGR Sensor Position Issues.
P0420, P0432: Catalyst System Efficiency Below Threshold (Bank 1 & Bank 2).
P0441, P0442, P0455, P0456: Evaporative Emission Control System (EVAP) Leaks (various sizes).
P0443: Evaporative Purge Flow System Solenoid Circuit Malfunction.
P0460, P0462, P0463: Fuel Level Sensor Circuit Issues.
P0500: Vehicle Speed Sensor Malfunction.
P0505: Idle Air Control System Malfunction.
P0522, P0523: Oil Pressure Sensor/Switch Low/High Voltage.
P0600, P0601, P0604, P0605: Internal Control Module (PCM/ECM) Errors.
P0700: Transmission Control System Malfunction (often requires further transmission-specific codes).
P0703: Brake Switch Circuit Malfunction.
P0711, P0712, P0713: Transmission Fluid Temperature Sensor Circuit Range/Performance Issues.
P0720: Output Shaft Speed Sensor Circuit Malfunction.
P0740: Torque Converter Clutch Circuit Malfunction.
P0743, P0748, P0753, P0756, P0783: Transmission Solenoid Circuit Issues (various solenoids).
P0833: Clutch Pedal Switch Circuit Malfunction.
P1192, P1193: Inlet Air Temperature Sensor Circuit Range/Performance Issues.
P1194, P1195, P1196, P1197: Oxygen Sensor Heater Performance/Slow Response (various banks and sensors).
P1198, P1199: Radiator Coolant Temperature Sensor Circuit Range/Performance Issues.
P1281: Engine is Cold Too Long.
P1282: Fuel Pump Relay Circuit Malfunction.
P1288, P1289: Intake Manifold Tuning Valve/Solenoid Circuit Issues.
P1290, P1292, P1293: Compressed Natural Gas System Pressure Sensor Issues.
P1294: Target Idle Speed Not Reached.
P1295, P1296: Throttle Position Sensor/MAP Sensor Low Voltage.
P1297: MAP Sensor Stuck – No Change During Run.
P1298: Lean During Wide Open Throttle.
P1299: MAP/TPS Inconsistent – Vacuum Leak.
P1388, P1389: Auto Shutdown Relay Circuit Problems.
P1390, P1391: Cam/Crank Sensor Signal Issues.
P1398, P1399: Crank Sensor Issues.
P1403: EGR Position Sensor Voltage Low.
P1476, P1477: Secondary Air Injection Issues.
P1478, P1479, P1480, P1481, P1482, P1483, P1484, P1485, P1486, P1487, P1488, P1489, P1490, P1491, P1492, P1493, P1494, P1495, P1496, P1498: Various Fan Relay, Solenoid, and Sensor Circuit Problems (Cooling, Air Injection, EVAP, etc.).
P1594, P1595, P1596, P1597, P1598, P1599: Speed Control and A/C Pressure Sensor Issues.
P1681, P1682, P1683, P1684, P1685, P1686, P1687, P1693, P1694, P1695, P1696, P1697, P1698, P1719, P1740, P1756, P1757, P1762, P1763, P1764, P1765, P1899: Communication and Control Module Issues (Cluster, Charging, Immobilizer, Transmission, etc.) and Transmission Specific Solenoid/Switch Problems.

Disclaimer: This code list is intended as a guide for troubleshooting. It is not exhaustive and may not be completely accurate for every Jeep Grand Cherokee model year or specific situation. Diagnostic trouble codes are indicators of potential problems, but they do not pinpoint the exact cause in every case. A code might suggest a faulty sensor, but the actual issue could be with wiring, connectors, or the system the sensor is monitoring.

Conclusion

Understanding and retrieving OBD2 codes on your Jeep Grand Cherokee is a valuable first step in diagnosing car problems. Using the “key trick” can provide a quick, basic code readout, while OBD2 scanners offer more in-depth diagnostics. However, remember that these codes are aids in troubleshooting, not definitive repair instructions.

It is crucial to use these codes as a starting point for further investigation. Consulting a reliable repair manual specific to your Jeep Grand Cherokee model and year, or seeking the expertise of a qualified mechanic, is highly recommended for accurate diagnosis and proper repair. Attempting repairs based solely on code readings without proper knowledge can sometimes lead to further complications. Empower yourself with information, but always prioritize professional guidance when it comes to vehicle repair.

Source: Adapted and expanded from an original compilation by ThePhantum on JeepHorizons.com. Please note that this list is compiled from various sources and accuracy is not guaranteed. It is intended for informational purposes and should not be used as a repair manual.