My 1997 Dodge Ram won't start and the check engine light shows code P1389, indicating an issue with the Anti-Theft System (ASD) relay. I'm wondering whether this is caused by a faulty ASD relay or if it's actually a problem with the Powertrain Control Module (PCM). Can anyone confirm what the most likely cause is and how to diagnose it?
I purchased my '99 Dakota used with an aftermarket command start system that worked perfectly initially. However, after installing an immobilizer required by insurance, the command start became nearly useless—requiring a key fob to be held close to the steering column to start the truck. The fob had buttons for start, lock, and unlock, along with a panic button. Since my truck lacks power locks, I initially thought the lock function was irrelevant. However, I recently discovered that pressing the 'lock' button triggered a flashing blue light (without an alarm system), and the truck would not crank at all. Pressing the 'unlock' button turned off the light and allowed normal starting. This suggests the command start system may be using the ASD module to prevent startup when the vehicle is in 'locked' mode. Could this behavior trigger P1389 when attempting to start after locking? It's a plausible theory worth investigating.
Check under the hood in the fuse box for the starter relay. If it’s damaged or burned, there may be no power reaching the starter, which could prevent starting. If that’s not the issue, inspect all wiring connections to the starter—ensure they are secure and tight.
Loose wires to the starter do not typically generate a P1389 code. The P1389 fault is specifically related to the ASD system, so this issue should be investigated through relay testing or circuit diagnostics rather than starter wiring.
Based on my experience, it's unlikely that either the relay or PCM alone is at fault. To test the ASD relay, locate it in the fuse box under the hood. Swap it with another identical relay—such as one for wipers or horn—to see if the truck starts. If it does, then you’ve identified a faulty relay. If not, the issue likely lies in the wiring or circuit connected to the ASD module.