AutoCodes – Jeep – P1398 Jeep

P1398 Jeep Code - Misfire Adaptive Numerator At Limit Condition

Quick Answer

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. Common causes include Faulty Crankshaft Position (CKP) Sensor, Crankshaft Position (CKP) Sensor harness is open or shorted, Crankshaft Position (CKP) Sensor circuit poor electrical connection. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: P1398 Jeep indicates Misfire Adaptive Numerator At Limit Condition.
Common causes: Common causes include Faulty Crankshaft Position (CKP) Sensor, Crankshaft Position (CKP) Sensor harness is open or shorted, Crankshaft Position (CKP) Sensor circuit poor electrical connection.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 11,059

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Aug 18, 2019

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
Comments
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Code P1398 Jeep Description

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.

OBDII Code P1398 Jeep - Misfire Adaptive Numerator At Limit Condition - AutoCodes.com — P1398 Jeep Code - Misfire Adaptive Numerator At Limit Condition

What does this mean?

What are the Possible Causes of the DTC P1398 Jeep?

Faulty Crankshaft Position (CKP) Sensor
Crankshaft Position (CKP) Sensor harness is open or shorted
Crankshaft Position (CKP) Sensor circuit poor electrical connection
Low cylinder compression

How to Fix the DTC P1398 Jeep?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What does this mean?

Code Tech Notes

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.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P1398 Jeep code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the P1398 Jeep code?

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.