P088 High Fuel Pressure Code

[darkness]

The part he mentioned it only revved to 2000 rpm, only stated duty cycle and amps. Figured that was all he took note of

Yup. I had to go back and read it again .

 

[LBZ]

I tried tapping the cruise switch but nothing happened. Not 100% but I don’t believe the idle up will work with an engine code active.

TBH I was leaning towards a stuck FPR myself. It was the 64mA that was throwing me for a loop. Also when I tinned it to the 2000 rpm IIRC the fuel pressure did not change. Neither desired nor actual.

I’m going to go to buddies shop on Friday with my laptop and spend a few hours on it and see what I can come up with. He lives 70 miles away so I only have time on my days off to look at it. Appreciate the input folks.

 

[gmduramax]

This probably won’t help. But I had a friend with an LBZ and his truck was doing exactly the same. His batteries were going bad and he replaced them per my request. Truck still had issues, reflashed the tune with EFI live and the problem went away and never came back. This was 8 years ago.

 

[LBZ]

Regulator unplugged desired matched close to actual, and plugged in went back to the way it was. Attached a pic of the codes.

 

[Chevy1925]

first pic of desired close to actual is with the regulator unplugged? if so, regulator is stuck. you should be seeing max rail pressure.

wouldnt hurt to just pull the little fuel line loop by the fprv to make sure its not popped open. get it running, unplug fpr and then pull the line. quick, make shift bottle test

 

[2004LB7]

64mA and unplugged should be wide open.

I wonder how the ECM measures the current. Since it uses PWM, does it average the value? Does it have a current sense resistor or induction loop? Or perhaps it's just calculated based on commanded duty cycle of the mosfet.

 

[LBZ]

So, thinking sticking regulator. Unplugged FPR no change, shut truck off restarted max rail, plugged in no change, rev it up and drops to 12k.

 

[2004LB7]

Do you have another ECM you can swap in? Or reload the tune as mentioned above?

 

[Chevy1925]

So, thinking sticking regulator. Unplugged FPR no change, shut truck off restarted max rail, plugged in no change, rev it up and drops to 12k.

yup, classic signs.

 

[LBZ]

Got an FPR enroute and old one out. Gonna clean all the soot and dirt out of everything and windmill it back together and see what happens.

I believe buddy does have access to both another ECM and TCM.

 

[LBZ]

Bad FPR. Only codes left are for the transmission number 2 solenoid stuck off and a low voltage code to the TCM. Project for another day…….

 

[Chevy1925]

Bad FPR. Only codes left are for the transmission number 2 solenoid stuck off and a low voltage code to the TCM. Project for another day…….

Probably ignition switch

 

[LBZ]

Probably ignition switch

You’re gonna have to elaborate on this one for me

 

[2004LB7]

Power for the TCM (and ECM) flow through the ignition switch. When the contacts get burned or dirty, the voltage to the TCM gets unreliable or has too large of a voltage drop and can cause the TCM to act up. Replacing the switch is not too difficult and doesn't require a new cylinder

 

[LBZ]

I did not know that. With as shitty as that ignition switch is I’m actually not surprised if that actually is the problem. Thanks folks!

 

[Chevy1925]

Yeah Mike taught me that years ago. Usually verified by the voltage out but if the ignition is shotty, I’d just replace it

 

[LBZ]

Found an open in the power wire and a green pin in the TCM connector on the harness side. Repaired wire, replaced the pin. All good now. Just abs codes left.

285/45R22 tires coming, 22.5 alcoas have been milled down so it’s going to be sweet. Tow tune and send it.