Encountering error codes in your Jeep Cherokee can be frustrating, but with the right tools and knowledge, you can effectively diagnose and resolve these issues. If you’re facing a P1398 or code 42 on your 1997 Jeep Cherokee, a tool like the Ch6000 Scan Tool, also known as the DRB III®, can be invaluable. This article will guide you through understanding these codes and how the CH6000 scan tool can assist in pinpointing and fixing the problems.
Understanding Error Code P1398: The Crank Sensor Calibration Issue
Error code P1398, or sometimes displayed as $BA, indicates “No Crank Sensor Learn” on 1996-1997 Jeep Cherokee models and other Chrysler vehicles of that era. This issue is often not a problem with the crank sensor itself, but rather a software glitch within the Powertrain Control Module (PCM).
According to Technical Service Bulletin (TSB) 25-003-01 from DaimlerChrysler Corporation, this erroneous DTC P1398 can occur due to a momentary voltage drop to the PCM. This can be triggered by normal or higher electrical loads, especially when the battery is marginal or electrical connections are poor. Cold weather or extended periods of vehicle inactivity can exacerbate this condition.
Alt: Authorized Software Update Label indicating PCM reprogramming information for Chrysler vehicles.
The TSB specifies that if your PCM software is older than calibration level 96Cal18 or 97Cal18, reprogramming the PCM with updated software is the recommended solution. This is where the CH6000 scan tool (DRB III®) comes into play. As outlined in the TSB’s “EQUIPMENT REQUIRED” section, the CH6000 is a necessary tool for this PCM reprogramming procedure.
Alt: Authorized Modification Label to be attached near the VECI label after PCM reprogramming as per TSB guidelines.
Using the CH6000 Scan Tool for PCM Reprogramming:
The TSB explicitly mentions using the CH6000 scan tool (DRB III®) along with the MDS2 (Mopar Diagnostic System) and necessary cables (CH7035, CH7000/7001) to reprogram the PCM. This process involves:
- Connecting the CH6000 scan tool to your Jeep Cherokee’s diagnostic port.
- Using the MDS2 software (at CIS CD 2077 or higher) to interface with the vehicle’s PCM.
- Following the on-screen prompts to selectively erase and reprogram the PCM with the updated software calibration (96Cal18 or 97Cal18).
It’s crucial to follow the TSB instructions precisely and ensure you have the correct software and equipment. After reprogramming, any DTCs set in other modules due to communication loss during the process should be cleared using the CH6000 scan tool. Always erase PCM faults last.
Decoding Error Code 42: Addressing the ASD Relay
Error code 42 in your Jeep Cherokee typically points to an issue with the Automatic Shutdown (ASD) relay circuit. The ASD relay is a critical component in the engine management system, providing power to vital engine components like the fuel injectors, ignition coil, and PCM.
A code 42 can arise from various factors within the ASD relay circuit, including:
- A faulty ASD relay itself.
- Wiring issues in the ASD relay circuit (shorts, opens, or corrosion).
- PCM driver malfunction (less common).
Troubleshooting Code 42 with Basic Steps:
A simple first step to address code 42 is to replace the ASD relay. The ASD relay is usually located in the power distribution center (fuse box) under the hood. You can often try swapping it with an identical relay from another less critical system (like the horn relay, if it’s the same type) to see if the code clears.
While a relay swap can sometimes resolve the issue, a CH6000 scan tool can be helpful in further diagnosis if the problem persists. It allows you to:
- Read detailed fault codes: Confirm the code is indeed related to the ASD relay circuit and check for any additional related codes.
- Monitor live data: Observe the status of the ASD relay and related sensors in real-time to identify intermittent issues.
- Perform actuator tests: Potentially activate the ASD relay via the scan tool to test its functionality and circuit integrity.
Why a Scan Tool Like CH6000 is Essential for Diagnosis
While basic troubleshooting steps like relay replacement are useful, a scan tool like the CH6000 (DRB III®) offers significant advantages for diagnosing complex automotive issues like those indicated by P1398 and code 42:
- Accurate Code Retrieval: Scan tools provide precise, alphanumeric codes (like P1398) which are far more informative than generic two-digit codes obtained through key-on/key-off methods.
- In-depth Diagnostics: Beyond just reading codes, scan tools like the CH6000 can access a wealth of diagnostic information, including live sensor data, actuator tests, and module-specific information.
- PCM Reprogramming Capability: For issues like P1398, which require PCM software updates, a compatible scan tool like the CH6000 is indispensable.
- Time Savings: By quickly and accurately pinpointing the source of the problem, a scan tool can save considerable time and guesswork compared to manual troubleshooting methods.
In conclusion, for Jeep Cherokee owners dealing with error codes like P1398 and 42, investing in or having access to a CH6000 scan tool (DRB III®) can be a game-changer. It not only aids in accurately diagnosing these specific issues but also provides a comprehensive diagnostic capability for a wide range of automotive problems, empowering you to maintain your vehicle effectively.
