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1998 Dodge 5.9L Engine Surges and Hesitation with P1391 Code - Cam Position Sensor Diagnosis

Model: 1998 dodge 5.9 Fault Code: P1391 Posted: 2012-10-21 16:33

A friend's 1998 Dodge 5.9L pickup, with over 200,000 miles, is experiencing recurring driveability issues including idle surging, hesitation during acceleration, and occasional stalling. The vehicle has recently started displaying a persistent Diagnostic Trouble Code (DTC) P1391. Despite recent maintenance—including replacement of spark plugs, wires, distributor cap, rotor, and the crankshaft position sensor (CKP)—the symptoms persist. The user is wondering whether the cam position sensor (CMP) might be the root cause given that P1391 specifically relates to the camshaft position sensor. The issue manifests at idle with surges and instability, while driving it hesitates and surges intermittently. The user seeks confirmation on whether focusing on the CMP sensor is a valid troubleshooting step. Additionally, they are concerned about the timing of when the P1391 code appeared—after installing an aftermarket crankshaft position sensor—raising questions about potential compatibility or signal integrity issues.

Related fault codes

P1391

Comments (5)

Anonymous 2012-10-22 09:29

On a vehicle with 200,000 miles, the engine is likely to have wear-related issues. However, be sure to inspect the cam position sensor (CMP) harness and connectors for damage—look for frayed wires, chaffing, corrosion, or loose connections. The vehicle may run in default mode if the CMP is missing, but performance will degrade significantly. Do not adjust the distributor housing as this can worsen misfires.

Anonymous 2012-10-22 13:28

Consider installing a genuine Mopar crankshaft position sensor (CPS) before performing extensive repairs. Aftermarket sensors are known to have inconsistent air gaps, which can result in corrupted signals and trigger the P1391 code. A dealer-grade sensor often resolves this issue without requiring major disassembly.

Anonymous 2012-10-22 15:33

Thanks for the input! The crankshaft position sensor was installed by a mechanic using an aftermarket unit. I noticed that the P1391 code did not appear before this replacement—prior codes were P0320 and P07??, neither of which triggered the Check Engine Light (CEL). This suggests the new sensor may be causing the P1391 fault. I’ve advised my friend to inspect all wiring and connectors for both the crank and cam sensors. The driveability issues have remained consistent before and after the sensor replacement.

Anonymous 2012-10-23 07:18

If there was no P1391 code prior to installing the new sensor, it's highly likely that the aftermarket crankshaft position sensor is responsible for triggering this fault—especially given its known signal quality issues.

Anonymous 2012-10-29 18:20

My friend recently installed a genuine dealer CPS and was told by the parts specialist that if the sensor were faulty, the truck would not start at all. However, the vehicle does run (though poorly), which makes me question whether this statement is accurate. Is it true that a bad crankshaft position sensor would prevent engine startup? Or could the parts representative have misunderstood the failure mode? Any clarification on this would be greatly appreciated.