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P0340, P0351, P0352, P1391 Fault Codes on 2002 Jeep Wrangler 4.0L Jasper Engine - Diagnosis & DIY Fix Tips

Model: Jeep 2002 Fault Code: P0340 Posted: 2007-03-08 17:53

I own a 2002 Jeep Wrangler with a 6-cylinder engine and manual transmission. The vehicle has recently triggered several OBD-II diagnostic codes: P0340 (Camshaft Position Sensor Circuit Malfunction), P0351, P0352 (Ignition Coil Set Faults), and P1391 (Fuel Pump Control Circuit Issue). I've already had the dealership replace the coil pack, camshaft position sensor, crankshaft position sensor, and spark plugs. The engine has experienced sudden surging and complete loss of power while driving at 70-75 mph. On one occasion, it stalled on the expressway—after turning off the engine and restarting, it ran normally for the remainder of the trip. The engine is a Jasper 4.0L installed two years ago with approximately 25–30,000 miles. I'm seeking affordable troubleshooting options to avoid further dealership expenses. I suspect mechanical wear or wiring issues rather than sensor faults, especially given that the original engine was hydro-locked due to a loose intake elbow and water ingress. The replacement Jasper engine is a long block, and I've logged 30K miles on it without prior issues. Any insights into possible root causes—such as distributor internal wear, wiring harness faults, or PCM malfunction—would be greatly appreciated. I'm particularly interested in cost-effective DIY solutions like ASD relay swaps or distributor inspection before investing in expensive parts.

Related fault codes

P0340P0351P0352P1391P3053

Comments (6)

Anonymous 2007-03-09 09:00

When the camshaft sensor was replaced, did they replace the entire distributor assembly or just the sensor plate and pickup? Was the engine a short block or long block? What was the original reason for swapping out the engine? Did all these codes appear after the replacement?

Anonymous 2007-03-09 14:18

I hydro-locked the original engine. The Jasper 4.0L installed is a long block. I've driven about 30,000 miles on it without issues before any problems arose. Only the camshaft sensor was replaced—there's no 'plate' in the traditional sense; they did replace the pickup (the small gray cap).

Anonymous 2007-03-09 16:18

Did they replace the full distributor assembly or just the internal plate within the distributor body? Gear teeth and bushings inside the distributor can wear over time, especially on older 4.0L engines—this often leads to erratic codes like P0340 or P0351. Also consider wiring faults in the injector, coil, cam, and crank sensor circuits—all of which are part of the ASD circuit. Start by swapping the ASD relay with a known good one from the fuse box. A faulty PCM is possible, but given that the vehicle only encountered water ingress through a loose intake elbow—not prolonged submersion—I'd prioritize checking the distributor or wiring first. If available, testing a used PCM or using an original warranty could also help. Was the PCM exposed to water for several hours?

Anonymous 2007-03-12 08:41

The PCM was never submerged. I hit a small water hole and water entered through a loose intake elbow. The vehicle was pulled out quickly. I removed the camshaft sensor and gently wiggled the distributor—what is the acceptable amount of play? I also inspected and cleaned all ground connections and wiring harnesses; no visible issues were found. I plan to try swapping the ASD relay next.

Anonymous 2007-03-12 08:49

It's difficult to quantify the exact amount of distributor play—it’s more about feel than measurement. You could compare it with a re-manufactured unit or simply replace the distributor assembly while it's out. How do the gear teeth look? Are they sharp and intact?

Anonymous 2007-03-12 11:32

I haven't yet removed the distributor. I'm planning to swap the ASD relay first, as a simple and low-cost test. I'm leaving for vacation tomorrow and will have a mechanic inspect it during my absence. Thank you all for your helpful input!