1997 K1500 p1351

Greetings,

I hope everyone is well.

Please help. I'm at my wits end with this one.

Iv'e got a 1997 Chevy Silverado Extended Cab Stepside that keeps throwing p1351. Which is a code indicative of high voltage at the Ignition Control Module.

I've changed the Ignition Control Module and the Ignition Coil and the code still comes up.

The code being thrown is always directly related to a low voltage issue I'm having.

When I first start the truck my volt gauge in the truck reads 14 straight up. 5 minutes later it's down below 10. If I shut the truck off and try and start it then, it will crank and start and die immediately. That is when the code gets set. Then I start it up and she runs fine. Every time. I have never not been able to get it to start.

I've got a brand new battery, brand new engine, Alternator checks out and is fine. When I bought the truck 2 years ago the seller claimed he had just put in a new fuel pump as well.

Here's some more weird info on the fuel system: Seller claimed a new fuel pump. Ok. Checks out. Like 58 lbs when engine is running. Key on ignition off and I hear it run for 2 seconds. Here's where it gets weird. By accident I discovered that my fuel pump relay was doing nothing. Truck starts and runs without the fuel pump relay in. But the fuel pump is operating as it should.......????

I've also checked every ground I could find. Everything checks out.

Thoughts? Power and ground checks out at the pump relay but even with the fuel pump relay out, it still starts and runs...

Any thoughts would be greatly appreciated.

Thank you

-Justin

jburns989592 wrote: When I first start the truck my volt gauge in the truck reads 14 straight up. 5 minutes later it's down below 10.

Does your battery light come on in instrument cluster when this drop in voltage occurs? Can you reproduce this in park and check alternator output when it's doing this?

As for why your fuel pump runs with the relay out, it's normal.
GM oil pressure switch @14:51