Review the 'Possible Causes' mentioned above and visually examine the corresponding wiring harness and connectors. Ensure to check for any damaged components and inspect the connector pins for signs of being broken, bent, pushed out, or corroded.
There is a factory service bulletin for the following models:
1997 Wrangler
1996-1997 Cherokee
1996-1997 Grand Cherokee
NOTE: THIS BULLETIN APPLIES TO VEHICLES EQUIPPED WITH A GASOLINE ENGINE.
SYMPTOM/CONDITION:
A customer may experience a MIL (Check Engine Lamp) illumination due to an erroneous DTC P1398 - No Crank Sensor Learn. This DTC may also be displayed as a $BA - Adaptive Numerator at Limit. This condition may be caused by a momentary drop in the supply voltage to the powertrain control module.
This condition may occur when a normal, or higher, electrical load is applied to the battery. A momentary drop in the supply voltage to the PCM may be caused by a marginal battery or poor electrical connections from the battery to the PCM. The condition may be further aggravated by cold ambient temperatures or when the vehicle has been left unused for an extended period of time.
To diagnose the P1398 Jeep code, it typically requires 1.0 hour of labor. The specific diagnosis time and labor rates at auto repair shops can differ based on factors such as the location, make and model of the vehicle, and even the engine type. It is common for most auto repair shops to charge between $75 and $150 per hour.
The Engine Control Module (ECM) has detected the actual crank sensor position does not agree with the expect crank sensor position.
With the engine running, the Powertrain Control Module (PCM) detects that the Actual Crankshaft Position (CKP) sensor signal level disagreed with the Expected CKP sensor signal level.
Need more information on how to fix the P1398 Jeep code? Get Access to Factory Service Manuals
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