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1997 sts
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Discussion Starter #1
I have gained a lot of help here over the years and wanted to add something that hopefully saves someone a little aggravation.

For several months my 97 STS had a P0174 code that would periodically be current then history (the SEL would never turn off). I checked/replace everything but couldn't get it to go away. I then started to experience either stalls or cranking with no start, a message that said "service Fuel System" and a P0231. I would wiggle some wires near the fuel pump relay and it would start. Well I found the culprit was the ignition relay. Why this would cause a P0174 is unknown to me. Once I replace the ignition relay (not the fuel pump relay) the SEL went out, my codes are gone and the car starts and runs great. I found the problem by confirming there was no power to the fuel pump fuse when the "no start" issue would strike. Power is supplied to this fuse by the ignition relay.
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
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19,265 Posts
I have gained a lot of help here over the years and wanted to add something that hopefully saves someone a little aggravation.

For several months my 97 STS had a P0174 code that would periodically be current then history (the SEL would never turn off). I checked/replace everything but couldn't get it to go away. I then started to experience either stalls or cranking with no start, a message that said "service Fuel System" and a P0231. I would wiggle some wires near the fuel pump relay and it would start. Well I found the culprit was the ignition relay. Why this would cause a P0174 is unknown to me. Once I replace the ignition relay (not the fuel pump relay) the SEL went out, my codes are gone and the car starts and runs great. I found the problem by confirming there was no power to the fuel pump fuse when the "no start" issue would strike. Power is supplied to this fuse by the ignition relay.
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I found the culprit was the ignition relay.
Why this would cause a P0174 is unknown to me.

it can't -
you have a vacuum leak in the front bank of cylinders -
probably the PCV hose -
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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68,441 Posts
P 0174 is a fuel/air mixture fault. It's entirely possible that the fuel pump and/or ignition circuits were throwing off the fuel ratio and it set a mixture code - O2 sensor did its work
 
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