Map throwing P0641 and no start
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Joined: May 2021
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Map throwing P0641 and no start Hi Everyone,
First off thank you so much to this community. I've been tackling my first ever engine swap leveraging this website any time I run into an issue. Fortunately, most of my issues have been relatively simple to diagnose and find solutions mostly using this forum.
I'm running an Erod (6.2L LS3). This motor is brand new and was run at the original builder I purchased it from. I've done no mods and followed instructions as carefully as I could. Went to fire the engine the first time, and it would not fire. It would try but never catch. I would get 2 codes. One is for a crankshaft learning, P0315 which seems normal for a new build. The second was a P0641 (Sensor Reference Voltage "A" Circuit/Open). After a lot of research, probing and checking different things, I concluded it was something with the MAP sensor. MAP plugged in, I get the P0641 code. No MAP and the P0641 code goes away and I get a P0107 MAP/Barometric Pressure Circuit Low Input. Since these are not too expensive, I figured just buy a new one and move on. Picked up a new AC Delco MAP (PN 55573248) plugged it in and still no fire. In my haste and frustration, I unplugged the MAP and tried it. Started right up with no hesitation. Engine idles fine, I have throttle response and everything seems normal but I have not tried to drive the vehicle at all.
I know this motor has an adapter for the MAP and as far as I can tell all Erod's came with it because some adapter is listed in the parts list. Looking at the adapter itself, I noticed 2 of the wires switch which I'm guessing is the purpose for the adapter. Visually the colors match what I find on the internet for an LS3 MAP adapter pigtail? I probed the wires and get a 5V signal from the harness. If I probe another 5V sensor with the MAP plugged in, it also reads 5V. Anyway I'm stumped. Could I have 2 bad MAP sensors? I suppose something could be up with the harness, but the engine was run with the harness installed and it was never taken off during the install. What else can I check and what else would you want to know about my setup?
First off thank you so much to this community. I've been tackling my first ever engine swap leveraging this website any time I run into an issue. Fortunately, most of my issues have been relatively simple to diagnose and find solutions mostly using this forum.
I'm running an Erod (6.2L LS3). This motor is brand new and was run at the original builder I purchased it from. I've done no mods and followed instructions as carefully as I could. Went to fire the engine the first time, and it would not fire. It would try but never catch. I would get 2 codes. One is for a crankshaft learning, P0315 which seems normal for a new build. The second was a P0641 (Sensor Reference Voltage "A" Circuit/Open). After a lot of research, probing and checking different things, I concluded it was something with the MAP sensor. MAP plugged in, I get the P0641 code. No MAP and the P0641 code goes away and I get a P0107 MAP/Barometric Pressure Circuit Low Input. Since these are not too expensive, I figured just buy a new one and move on. Picked up a new AC Delco MAP (PN 55573248) plugged it in and still no fire. In my haste and frustration, I unplugged the MAP and tried it. Started right up with no hesitation. Engine idles fine, I have throttle response and everything seems normal but I have not tried to drive the vehicle at all.
I know this motor has an adapter for the MAP and as far as I can tell all Erod's came with it because some adapter is listed in the parts list. Looking at the adapter itself, I noticed 2 of the wires switch which I'm guessing is the purpose for the adapter. Visually the colors match what I find on the internet for an LS3 MAP adapter pigtail? I probed the wires and get a 5V signal from the harness. If I probe another 5V sensor with the MAP plugged in, it also reads 5V. Anyway I'm stumped. Could I have 2 bad MAP sensors? I suppose something could be up with the harness, but the engine was run with the harness installed and it was never taken off during the install. What else can I check and what else would you want to know about my setup?
