2006 Chevy C4500 code P0088

FordFanaticTony · December 19, 2014

Hey fellas Ford Diesel Tech with first duramax. I have a code P0088 and was able to look at pids and found at idle my actual fuel pressure to be at 12,000 pis when desired wants it to be at 5,300. Someone here replaced the regulator and harness last week but still has a code P0088. just wondering if the frp sensor could be bad. Any suggestions? Thanks for any help guys.

amailloux · December 20, 2014

What is fuel pressure koeo? Look at the main harness where it crosses the top of the engine. It gets mashed when braking and damages the harness badly. How does it sound, if the fuel pressure is actually high, you should have a little clatter and light smoke on a dmax. The regulator on the high pressure pump was replaced, and the short jumper harness? Frp should be around 38 percent or so at idle. Have seen some terminal issues at the big bale connectors cause skewed readings also.

8WA Sman · December 20, 2014

+1 on checking terminal tension at the two bulkhead connectors at the right valve cover. Especially if it has a chip harness T in.

FordFanaticTony · December 22, 2014

regulator and pigtail were replaced.. the koeo is at 71 psi

DieselD · December 23, 2014

Kill it with fire! :flamethrower:

I really dislike working on these. We have far too many in our fleet and I cant wait until they all die or get auctioned! dmax in a pickup not too bad, dmax in a kodiak :banghead:

With that said most of my issues tend to be wiring related, injectors and fuel pumps are pretty common too.

FordFanaticTony · December 23, 2014

So for the high fuel pressure it wouldnt be a fuel pressure sensor or a defetive regulator causing the P0088

amailloux · December 24, 2014

Could be. 1st, grab the scan tool and then you have to listen to the engine. Monitor desired and actual as well as Frp percent. Use the scan tool to command fuel pressure to 160 mpa and see if the relief valve opens. If it does, the pressure will drop drastically, and the engine should quiet down. This can prove a skewed sensor. You have to determine if the pressure is actually high or not first. Resistance in the circuit will skew the readings high if I remember correctly. The 1 regulator on the back of the high pressure pump controls pressure. On an 06, they had very few failures, especially for p0088. I have seen them stick, and have actually used the gm cleaning procedure with success where you run 16 ounces of top engine cleaner and 1 gallon of fuel and run off of this mixture. Takes nearly 2 hours. If the regulator sticks you will have p0088 at idle and p0087 under load. This can be intermittent. Also load test all 3 circuits from the ECM to the sensor. Tons and tons of wiring problems.

8WA Sman · December 24, 2014

Alan thanks for the insight on diagnosing a skewed sensor. And the tip about top engine cleaner, didn't know it could be used on a diesel.

Matt Saunoras · January 14, 2015

Got a call today on a 2006 GMC 5500 32 passenger bus. Guy said it had a P0007, P0200 and a P0088 in it. Runs like crap, won't go over 65mph.

I don't have the vin, is an 06 an LLY or LBZ?

amailloux · January 14, 2015

Could be either depending only on calibration. Hardware is all the same. I call 06 lbz engines.

Matt Saunoras · January 14, 2015

Thanks. Should I even waste my time without any way to monitor pid data? I know you emphasized wiring problems and that's what my first instinct tells me.

amailloux · January 15, 2015

You really need to be able to monitor desired, actual, and Frp percent.

Matt Saunoras · January 16, 2015

I may be able to borrow a snap-on scan tool for the job. It's a bus owned by the ambulance company I do work for so I'll see what they want to do tomorrow. They know I might not be able to do anything with it.