Hey Scotty I have a 98 GMC Sierra 1500 that keeps popping up the p1351 code and I’ve done some research on it and I noticed that that one of the symptoms was whenever the outside temperature gets really hot it doesn’t start the first time but it always starts the second time you turn the key. The first time you try and start it, it will crank over and run like crap for a second then it will die and when you cycle the key over again it starts right up.
That P1351 sure makes the ICM (Ignition Control Module) or the Crank sensor likely culprits, but by your symptoms that doesn't sound like what's happening here.
What you're describing at startup sounds more like a fuel starvation issue.
(the P1351 code could be the result of prolonged cranking times because battery voltage to the ICM falls during cranking.) ((The P1351 code should be interpreted as "abnormal voltage", not necessarily "high voltage")).
Back in 1998 GM had a pretty unique fuel pump circuit.
It had the fuel pump relay to control power to the fuel pump. (the PCM controlled it and used it to "prime the fuel system" for a few seconds Key ON as well as control the fuel pump during engine running).
But it also had a 2nd Oil Pressure sender. (more of an oil pressure switch) located in the back of the engine by the firewall.
That 2nd Oil Pressure Sender/switch was also part of the fuel pump circuit.
When sufficient engine oil pressure was reached it would close that 2nd Oil Pressure Sender/switch, and it would provide direct power to the fuel pump even if the Fuel Pump Relay failed.
So, could it be possible that the fuel pump relay has failed and isn't priming the fuel lines when you turn the key to ON and then as you crank the engine, oil pressure is building up enough to to close that oil pressure switch to finally send power to the fuel pump?
Cold oil = higher oil pressure so maybe the oil pressure builds up faster in the cold weather and slower in the hot weather during cranking.
It should be easy to confirm this theory or "blow it out of the water".
Turn the Key to ON. Do you hear the fuel pump running for a couple of seconds? If you do, the fuel pump relay is working.
If that's the case you should put a fuel pressure gauge on it and check how much fuel pressure is being "primed" during those few seconds when you turn the key to ON.
Notice the Grey wire from the fuel pump relay to the fuel pump. See how that Oil Pressure Sender/switch's Grey wire is connected into the circuit and can bypass the relay to provide power to the fuel pump when sufficient oil pressure closes its switch even if the Fuel Pump Relay is Open?
Thank you!! I put a new fuel pump in it about a year ago because the old one finally gave out. I will definitely run a fuel pressure test on it.
Hoping your problem is solved. I have similar issue with my VW eos and now key not turning at all and I need to start my car. Please help with any advices.