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P1634 - Ignition 1 Switch Circuit can not figure this code out 2 days now 97 Eldorado

13K views 7 replies 6 participants last post by  rodnok01 
#1 ·
Can not figure this one out, sets of mil light, battery tests good, cleaned ign 1 fuse and receptacle. I also cleaned battery connections thinking I had a voltage drop problem. If I clear code it will come right back within seconds of starting car. Please help can not pass emissions test with mil light lit. Just finished replacing head gaskets so motor/tranny was out. I believe it sets off code if voltage varies more than 2 volts. This is my only problem after doing such a big repair and it is bumming me out!
 
#2 ·
Looked at some wiring diagrams, car has something like 5 ignition feeds 2 from pcm and 3 from battery ign 1 feeds the icm which is the plate assy that coils sit on. Before I go get one anybody ever had the icm ignition control module go bad if so what king of demons did you encounter?
 
#5 ·
Just got this code after chasing down issues with my turn signal. The code only shows up under PCM menu. What are some things I can check? Car seems to start fine and idle fine, I cleared the code and it came right back. I didn't have this code before I learned how to check them from the "How to pull codes" sticky".

Thanks!
 
#6 ·
You might want to check the IGN 1 fuse in the underhood fuse/relay box. Corroded contact blade ?? Same for the IGN fuses in the rear fuse box.

Owner's manual for fuse box legends, or the sticker under each box top.

P 1634 is a Powertrain DTC. DTCs are prefixed with the general system they are associated with.

B = Body
C = Chassis
P = Powertrain
U = Volts and data transmission
 
#8 ·
OldStuff has a point, there are so many to be missed. The one under ICM is left off a lot, there is another large one on back of engine(Bill Buttermore left off) that goes to exhaust stud and another trans /engine rear area that several grounds goto. Main Ground is on front of engine as I'm sure you know.
 
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