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Jeep Wrangler YJ
YJ General Discussion
New ecm or pcm
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<blockquote data-quote="machoheadgames" data-source="post: 438077" data-attributes="member: 18789"><p>All I recall the PCM doing for the fuel pump is the PCM grounds the ASD (auto shut down) relay and I believe the fuel pump relay power runs through the ASD. The power for the injectors and the ignition coil also go through the ASD so if your PCM is no longer operating the ASD, you’d lose those as well. So you need to confirm that the ASD is your problem, since the PCM doesn’t control the fuel pump in any other ways….</p><p></p><p>As for the PCM, they can not be flashed. They’re ancient and programmed as they are. The good news is, it doesn’t matter. The only thing you need is a 91-95 4.0 computer. The auto version will not operate your shift light. The manual will. The only picky one is a 94-95 automatic. The 94-95 autos have a lockup torque converter and need a 94-95 automatic computer (2.5 or 4.0 specific) to operate the lockup converter. A manual trans can run any same-engine auto or manual computer, so you’ll be fine. But I still have my doubts about the PCM fixing the problem. I’ll have to look into the factory service manual again to refresh my memory on the connections between the PCM and the fuel pump to verify their relation.</p></blockquote><p></p>
[QUOTE="machoheadgames, post: 438077, member: 18789"] All I recall the PCM doing for the fuel pump is the PCM grounds the ASD (auto shut down) relay and I believe the fuel pump relay power runs through the ASD. The power for the injectors and the ignition coil also go through the ASD so if your PCM is no longer operating the ASD, you’d lose those as well. So you need to confirm that the ASD is your problem, since the PCM doesn’t control the fuel pump in any other ways…. As for the PCM, they can not be flashed. They’re ancient and programmed as they are. The good news is, it doesn’t matter. The only thing you need is a 91-95 4.0 computer. The auto version will not operate your shift light. The manual will. The only picky one is a 94-95 automatic. The 94-95 autos have a lockup torque converter and need a 94-95 automatic computer (2.5 or 4.0 specific) to operate the lockup converter. A manual trans can run any same-engine auto or manual computer, so you’ll be fine. But I still have my doubts about the PCM fixing the problem. I’ll have to look into the factory service manual again to refresh my memory on the connections between the PCM and the fuel pump to verify their relation. [/QUOTE]
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Jeep Wrangler YJ
YJ General Discussion
New ecm or pcm
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