12/12/2002
Owning a classic Dodge or Chrysler vehicle comes with a unique charm, but when the check engine light illuminates, it can feel like your cherished ride is speaking a foreign language. For models from 1995 and earlier, these vehicles utilise an OBD1 (On-Board Diagnostics Generation 1) system, which communicates issues through a series of flashes or numerical codes. Understanding these codes is the first crucial step in diagnosing and resolving engine problems, saving you both time and potential expense at the garage.
Unlike modern OBD2 systems that use a dedicated electronic scanner, many OBD1 Dodge and Chrysler vehicles allow you to retrieve diagnostic trouble codes (DTCs) right from your dashboard, often without any special tools. This guide will walk you through the simple process of reading these codes and provide a comprehensive list of what each one signifies. Whether you're a seasoned DIY mechanic or a car enthusiast looking to understand your vehicle better, this information is invaluable.
How to Retrieve Dodge/Chrysler OBD1 Codes
Before diving into the code list, you need to know how to get your vehicle to 'speak' its diagnostic messages. The most common method for Dodge and Chrysler OBD1 vehicles is known as the 'key cycling' or 'key on/off' method. This simple procedure allows the Powertrain Control Module (PCM) to flash the diagnostic codes on your dashboard's check engine light, or 'Malfunction Indicator Lamp' (MIL).
The Key Cycling Method: A Step-by-Step Guide
- Prepare Your Vehicle: Ensure your vehicle is switched off and in 'Park' (for automatics) or 'Neutral' (for manuals) with the parking brake engaged.
- Locate the Check Engine Light: Identify the 'Check Engine', 'Service Engine Soon', or 'Power Loss' light on your dashboard. This is the light that will flash the codes.
- Perform the Key Cycle: Insert your ignition key and turn it from the 'OFF' position to 'ON' (without starting the engine) and then back to 'OFF' three times rapidly, ending in the 'ON' position. The sequence is: OFF-ON-OFF-ON-OFF-ON.
- Observe the Flashes: The check engine light should begin to flash. Count the flashes carefully. For example, two flashes, a pause, and then three flashes would indicate code 23. A short pause separates digits within a code, and a longer pause separates different codes.
- Note Down the Codes: As the codes flash, write them down in the order they appear. Some vehicles will display codes multiple times, which can help confirm your count.
- End of Messages: The system will typically flash a specific code, often 55, to indicate the end of the diagnostic messages. Once you see this, you know you have all the stored codes.
It's important to be precise when counting the flashes. If you miss a flash or miscount, simply turn the ignition off and repeat the process. This method allows you to pull codes without an expensive OBD1 scanner, making it a truly DIY-friendly diagnostic approach.
Understanding Your OBD1 Codes
Once you've retrieved the codes, the next step is to understand what they mean. OBD1 systems primarily focus on engine and emissions-related issues. Each code corresponds to a specific sensor, circuit, or system that the PCM has detected an anomaly in. Remember, a single fault can sometimes trigger multiple codes, so it's often best to address the first code or the most severe issue identified.
Dodge/Chrysler OBD1 Diagnostic Trouble Codes (DTCs) - Domestic Vehicles (1995 & Prior)
The following table provides a comprehensive list of OBD1 codes commonly found in domestic Dodge and Chrysler vehicles from 1995 and earlier. Note that some codes may have multiple definitions depending on the specific model year or engine configuration. Always consult your vehicle's service manual for the most precise information.
| Code | Definition |
|---|---|
| 11 | Timing belt skipped 1 tooth or more from initial learned value; Intermittent loss of either camshaft or crankshaft position sensor; No crank reference signal detected during engine cranking; Crankshaft signal or ignition signal, no reference signal during cranking. |
| 12 | Direct battery input to PCM was disconnected within the last 50 key-on cycles (normal); Memory to controller has been cleared within 50-100 engine starts. |
| 13 | No change in MAP from start to run; MAP sensor vacuum, no change from start to run or output voltage does not equal throttle position. |
| 14 | MAP sensor voltage too low; MAP voltage too high or too low. |
| 15 | No vehicle speed sensor signal. |
| 16 | Knock sensor circuit, open or short detected. |
| 17 | Closed loop temp not reached or engine cold too long; Low engine temperature, possible thermostat fault. |
| 21 | O2 sensor problem (oxygen sensor), upstream or downstream; Oxygen sensor signal, neither rich or lean detected or O2 shorted to voltage; Knock sensor circuit (starting in 1989). |
| 22 | Engine coolant temp sensor out of range; Coolant temp sensor voltage low/high. |
| 23 | Intake air temp sensor out of range; Air charge temp sensor voltage high/low detected. |
| 24 | Throttle Position sensor out of range; Throttle position sensor voltage high/low. |
| 25 | Idle air control motor circuits, target idle not reached (+/- 200), vacuum leak found; Automatic idle speed motor driver circuit, short or open detected. |
| 26 | Injectors 1,2,3 peak current not reached; problem in injector control circuits cylinder 1 and/or 2. |
| 27 | Injector control circuit; Injector control circuit does not respond to control signal, problem in injector control circuits 3 and/or 4. |
| 31 | Evap purge flow monitor failure or evap solenoid circuit; Purge solenoid circuit, open or short detected. |
| 32 | EGR system failure; EGR solenoid circuit, open or short detected. |
| 33 | A/C clutch relay circuit, open or short detected. |
| 34 | Speed control Solenoid circuits; Speed control servo solenoid, open or short detected. |
| 35 | Rad Fan control relay circuit; Radiator fan control relay circuit, open or short detected. |
| 36 | Waste-gate solenoid, open or short detected. |
| 37 | Torque converter clutch solenoid CKT or park/neutral switch failure; Baro read solenoid; PTU solenoid circuit (starting in 1989). |
| 41 | Generator field not switching properly; Charging system circuit not responding to control signal, alternator field circuit not switching properly. |
| 42 | Fuel pump relay control CKT; Auto shutdown relay control CKT; No ASD relay output voltage at PCM; Fuel level sending unit volts out of range; Fuel level unit No change over miles; Fuel pump or auto shutdown (ASD) relay voltage sensed at controller; Z1 voltage sense. |
| 43 | Multiple/single cylinder misfire; Ignition control circuit not responding. |
| 44 | Battery temp sensor volts out of range; Battery temperature voltage circuit problem. |
| 45 | Turbo boost limit exceeded-map sensor detects over-boost. |
| 46 | Charging system voltage too low; Battery voltage too high...overcharging. |
| 47 | Charging system voltage too high; Battery voltage too low...battery voltage low or charging output low. |
| 51 | Fuel system lean; Air/fuel at limit; Lean exhaust indication, O2 voltage latched below .450 volts. |
| 52 | Fuel system rich; Rich exhaust indication, O2 voltage latched above .450 volts. |
| 53 | Internal control failure; Internal controller failure (normal code on a re-calibrated controller). |
| 54 | No Cam signal at PCM; Fuel sync signal not detected during cranking. |
| 55 | End of error messages (If you get this only, no errors were found). |
| 61 | Baro read solenoid, open or short detected. |
| 62 | PCM failure SRI mile not stored; EMR mileage not stored. |
| 63 | PCM Failure EEPROM write denied; EEPROM write denied. |
| 64 | Catalytic Converter Efficiency Failure; Flex fuel sensor signal out of range; VNT solenoid #1 circuit. |
| 65 | Power steering switch failure; Manifold tuning valve, open or short detected; VNT solenoid #2 circuit. |
| 66 | No CCD messages. |
| 76 | Ballast bypass relay, open or short detected. |
| 77 | Speed control relay, open or short detected. |
| 88 | Display used for start or test (will only be seen using a DRB2 scanner). |
Dodge/Chrysler OBD1 Diagnostic Trouble Codes (DTCs) - Import Vehicles
For certain import models under the Dodge/Chrysler umbrella, a different set of OBD1 codes may apply. These codes often point to similar system failures but use different numbering. Always cross-reference with your vehicle's specific service manual to ensure accuracy.
| Code | Definition |
|---|---|
| 1 | Oxygen sensor |
| 2 | Crank engine sensor |
| 3 | Air flow sensor |
| 4 | Barometric pressure sensor |
| 5 | Throttle positioner sensor |
| 6 | Motor position sensor |
| 7 | Engine coolant temperature sensor |
| 8 | No.1 cylinder TDC sensor |
| 12 | Air flow sensor |
| 13 | Air temperature sensor |
| 14 | Throttle positioner sensor |
| 15 | SC motor position sensor |
| 16 | Engine coolant temperature sensor |
| 21 | Engine coolant temperature sensor |
| 22 | Crank angle sensor |
| 23 | No.1 cylinder TDC sensor |
| 24 | Vehicle speed sensor |
| 25 | Barometric pressure sensor |
| 31 | Knock sensor |
| 32 | Manifold pressure sensor |
| 36 | Ignition timing adjustment signal |
| 39 | Oxygen sensor |
| 41 | Injector |
| 42 | Fuel pump |
| 43 | EGR |
| 44 | Ignition coil |
| 52 | Ignition coil |
| 53 | Ignition coil |
| 55 | IAC valve position sensor |
| 59 | Heated oxygen sensor |
| 61 | Transaxle control unit cable |
| 62 | Warm up control valve position sensor |
What to Do After Retrieving a Code
Finding a code is just the beginning of the diagnostic journey. Here's a general approach to tackling the issue:
- Verify the Code: If possible, repeat the key cycling method a couple of times to ensure you've read the codes correctly. Sometimes, transient issues can trigger a code that doesn't represent a persistent problem.
- Research the Definition: Use the tables above and your vehicle's specific service manual to understand the exact meaning of the code. Pay attention to any nuances or multiple definitions for the same code number.
- Initial Inspection: Begin with a visual inspection. Check the wiring, connectors, and vacuum lines related to the sensor or system indicated by the code. Look for obvious signs of damage, corrosion, or disconnections. A loose wire or cracked hose can often be the culprit.
- Consult a Service Manual: A detailed service manual for your specific year and model is an invaluable resource. It will provide circuit diagrams, testing procedures for components, and specific diagnostic flowcharts for each code.
- Test the Component: Based on the code, you might need to test the affected sensor or component. This could involve checking resistance, voltage, or continuity using a multimeter. For example, an oxygen sensor code (like 21 for domestic models) might require checking its heater circuit or signal output.
- Clear the Codes: After you've performed a repair, you'll want to clear the codes to see if the issue has been resolved. For most OBD1 systems, disconnecting the vehicle's battery for 15-30 minutes will clear the PCM's memory and extinguish the check engine light. Be aware that this will also reset your radio presets and any learned engine parameters, so the vehicle might drive slightly differently for a short period while it relearns.
- Test Drive: Take your vehicle for a test drive under various conditions (city, motorway) to confirm the repair. If the check engine light stays off, congratulations – you've likely fixed the problem! If it returns, you may need to re-evaluate your diagnosis or explore other potential causes.
Common OBD1 Issues and Their Remedies
While the list of codes is extensive, some issues appear more frequently than others in older Dodge/Chrysler vehicles:
- Oxygen Sensor (Code 21): Often indicates a rich or lean fuel condition. Check for vacuum leaks, faulty injectors, or a failing oxygen sensor itself. A thorough inspection of the exhaust system for leaks near the sensor is also advisable.
- MAP Sensor (Codes 13, 14): Manifold Absolute Pressure sensor issues can lead to poor fuel economy and performance. Check the sensor's electrical connection, its vacuum line for cracks or blockages, and test the sensor's voltage output.
- Engine Coolant Temperature Sensor (Codes 17, 22): A faulty ECT sensor can affect fuel mixture and idle speed. Verify its wiring and test its resistance at different temperatures. Code 17 specifically might suggest a stuck-open thermostat, leading to the engine running cold.
- Idle Air Control (IAC) Motor (Code 25): Common for rough idle or stalling. Inspect the IAC motor and its housing for carbon buildup, which can impede its operation. Cleaning the throttle body and IAC passage often resolves this. Look for vacuum leaks as well.
- Charging System (Codes 41, 46, 47): These codes point to issues with the alternator, battery, or voltage regulator. Test the battery voltage with the engine off and running, and check the alternator output.
- Fuel System (Codes 51, 52): Indicate lean or rich conditions. A lean condition (51) could be due to vacuum leaks, low fuel pressure, or a clogged fuel filter. A rich condition (52) might point to a leaky injector, a faulty oxygen sensor, or excessive fuel pressure.
Why is My Code 12 Normal?
One code that often causes confusion is Code 12. For many Dodge/Chrysler OBD1 systems, Code 12 indicates that the direct battery input to the PCM (Powertrain Control Module) has been disconnected within the last 50 key-on cycles, or that the controller's memory has been cleared. This code is considered normal if you've recently disconnected your car's battery (e.g., for maintenance or to clear codes). It simply tells you that the PCM's volatile memory has been reset and it's starting to re-learn engine parameters. If you haven't disconnected the battery and this code appears consistently, it could suggest an intermittent power supply issue to the PCM, but in most cases, it's nothing to worry about and will clear itself after a few drive cycles.
Essential Tools for OBD1 Diagnostics
While the key cycling method is convenient, having a few basic tools can significantly aid your diagnostic process:
- Digital Multimeter: Indispensable for checking voltage, resistance, and continuity in circuits and sensors. Many diagnostic procedures in a service manual will require a multimeter.
- Vacuum Gauge: Crucial for detecting vacuum leaks, which are a common cause of many engine performance issues and can trigger various OBD1 codes.
- Basic Spanner and Socket Set: For accessing and removing components for inspection or replacement.
- Wiring Diagrams: Found in service manuals, these are vital for understanding the electrical pathways of your vehicle's systems.
- OBD1 Scan Tool (Optional but Helpful): While not strictly necessary for reading codes via the key method, a dedicated OBD1 scan tool can often provide a more immediate and clear display of codes, and sometimes offer additional diagnostic capabilities depending on the model.
Frequently Asked Questions (FAQs)
Q: Will clearing the codes fix my car?
A: No. Clearing codes only erases the fault memory from the PCM and turns off the check engine light. It does not fix the underlying problem. The light will likely reappear if the fault persists. Always diagnose and repair the issue before clearing codes.
Q: Can a low battery cause OBD1 codes?
A: Yes, absolutely. Low battery voltage can cause erratic sensor readings and insufficient power to various control modules, leading to a variety of seemingly unrelated diagnostic codes. Always ensure your battery is fully charged and in good health before diagnosing electrical issues.
Q: How long do I need to disconnect the battery to clear codes?
A: Typically, 15 to 30 minutes is sufficient to ensure the PCM's memory is fully cleared. Some mechanics recommend longer, up to an hour, just to be safe.
Q: My check engine light is on, but I get Code 55 only. What does that mean?
A: Code 55 signifies the 'end of messages', meaning no active fault codes were stored at the time of the key cycling test. If your check engine light is still on, it might be due to a very recent fault that hasn't fully registered, or a bulb check, or a persistent issue that doesn't trigger a specific DTC. Sometimes, a fault may be intermittent and not present during the test cycle.
Q: Are OBD1 codes standard across all car manufacturers?
A: No, unlike OBD2 codes which are largely standardised, OBD1 codes are manufacturer-specific. A code 21 on a Dodge will mean something entirely different on a Ford or General Motors vehicle from the same era. This is why having manufacturer-specific lists like this one is so important.
Final Thoughts
Understanding and reading Dodge/Chrysler OBD1 codes empowers you to take control of your vehicle's maintenance and troubleshooting. While these older systems might seem less sophisticated than their modern counterparts, they provide crucial insights into your engine's health. By following the key cycling method, consulting the comprehensive code lists provided, and performing careful diagnosis, you can confidently address many common issues. Remember, consistent preventative maintenance is key to minimising engine problems and ensuring your classic runs reliably for years to come. Happy motoring!
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