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99 stratus 2 4L engine just died goin down road-had p0340 code- i am thinking computer everything is getting back to the computer-signal wise-ASD relay has 12 volts on it key off or on?

A P0340 code indicates a problem with the camshaft position sensor (CMP sensor). This sensor is crucial because the engine's computer (PCM or ECM) needs its signal to know the position of the camshaft relative to the crankshaft to time the fuel injection and ignition correctly. A faulty CMP sensor will prevent the engine from running.

Your suspicion that the computer is involved is reasonable, as it relies on the CMP sensor signal. However, a P0340 doesn't automatically mean the computer itself is bad. It's more likely the sensor, its wiring, or a connection issue.

Regarding the ASD relay (Auto Shutdown Relay):

* It should NOT have 12 volts on it with the key OFF. The ASD relay is powered only when the engine is running (or cranking). Having 12V constantly indicates a short circuit somewhere in the ASD relay circuit, which is a serious problem that needs immediate attention. This short could be damaging other components.

Troubleshooting Steps:

1. Check the CMP sensor itself: It's usually located on the engine near the camshaft. Inspect it for any physical damage (broken wires, cracked connector). Consider replacing it – they're relatively inexpensive.

2. Check the CMP sensor wiring and connector: Carefully inspect the wiring harness leading to the sensor for any breaks, shorts, or corrosion. Pay close attention to the connector itself – make sure it's clean and securely plugged in. Wiggling the connector while someone tries to crank the engine might reveal an intermittent connection problem.

3. Verify 12V at the ASD Relay: Double-check your 12V measurement at the ASD relay with the key OFF. If it *still* shows 12V, trace the wiring back to find the short circuit. This is a critical issue. A short can damage the ASD relay, the PCM, or even cause a fire.

4. Check other sensors: While the P0340 points to the CMP sensor, other sensors (crank position sensor, etc.) can sometimes indirectly cause similar symptoms. Have a mechanic scan your vehicle for *all* trouble codes.

5. Professional Diagnosis: If you're not comfortable with electrical diagnostics, take your car to a mechanic. A scan tool can provide more detailed information, and a professional can efficiently trace the short circuit if one exists. Ignoring the constant 12V on the ASD relay is risky.

The constant 12V on the ASD relay is the most concerning issue. Address that first to prevent further damage. The P0340 might be a consequence of the short, or it might be a separate issue. Don't try to start the engine until this is resolved.

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