Idaho XJ Guy
NAXJA Forum User
- Location
- Boise, ID
Long story short, I think my PCM is never going to sleep with the key off.
I have a 99 XJ 4.0 Auto that has had a power draw for years. It doesn't appear to be getting ang worse, but I've taken to just disconnecting the battery when it's parked. I'd like to fix it for good.
I'm measuring 1.89 amps of current with everything off. When I pull fuses 16 and 22 together from the PDC, the draw goes away. Similarly, if I disconnect the C107 connector at the rear if the engine, or the black PCM connector, the draw goes away.
That leads me to believe that it's my PCM that is eating power. I'm thinking one of two things is wrong. Either the PCM is staying "awake" at all times because... reasons, or the PCM is bad and is just eating power by existing.
I swapped in a PCM I had laying around from a 97 ZJ 4.0. I know it's not compatible with my XJ, but I wanted to see if the power draw remained. It did. And it was the same 1.89 amps.
So now I'm wondering if I have two PCMs that have failed similarly, or if they're both responding to some stimulus causing them to remain "awake" and consuming power at all times.
Does anyone know what is required for the PCM to go to sleep? Anyone experienced this kind of issue before? I'm not going to just buy a replacement PCM just to see if that fixes it. I believe in proper diagnosis first. Hoping someone here can help get me past this gap in my knowledge.
I have a 99 XJ 4.0 Auto that has had a power draw for years. It doesn't appear to be getting ang worse, but I've taken to just disconnecting the battery when it's parked. I'd like to fix it for good.
I'm measuring 1.89 amps of current with everything off. When I pull fuses 16 and 22 together from the PDC, the draw goes away. Similarly, if I disconnect the C107 connector at the rear if the engine, or the black PCM connector, the draw goes away.
That leads me to believe that it's my PCM that is eating power. I'm thinking one of two things is wrong. Either the PCM is staying "awake" at all times because... reasons, or the PCM is bad and is just eating power by existing.
I swapped in a PCM I had laying around from a 97 ZJ 4.0. I know it's not compatible with my XJ, but I wanted to see if the power draw remained. It did. And it was the same 1.89 amps.
So now I'm wondering if I have two PCMs that have failed similarly, or if they're both responding to some stimulus causing them to remain "awake" and consuming power at all times.
Does anyone know what is required for the PCM to go to sleep? Anyone experienced this kind of issue before? I'm not going to just buy a replacement PCM just to see if that fixes it. I believe in proper diagnosis first. Hoping someone here can help get me past this gap in my knowledge.
