02 Z71 Won't Stay Running

gnsgn1 · March 28, 2009

Hello all,

I'm a newbie here and have a problem. I have an 02 Z71 with the 5.3 vortec. The problem started a few days ago. I was driving on the highway at a steady 65 mph when the truck just died. No stutters, no warning lights, just shut off. I coasted to the shoulder and tried to restart but she would only turn over but not start. After a few minutes she started normally and I drove home, about ten miles with no problems. As soon as I pulled in my driveway she started to lose rpm and died again. My first thought was fuel pump so I checked fuel pressure and it had about 50 psi. I replaced the pump with a new one and also a new filter. Started it with no problems and let it idle for about thirty minutes and she died again. It was getting dark so I left it alone until the next day. Started normally again and ran again for about fifteen minutes and died again. I hooked up a fuel pressure guage and it still shows 50 psi. I do have a SES light that's been on since I washed the engine about a month ago. Stored codes are P0332 (knock sensor circuit low voltage bank 2) and P0420(catalyst efficiency below threshold). No other codes stored. What could be causing it to just die like this? The truck has 185k miles and runs great otherwise. Thanks in advance for any suggestions.

98 Z71 SLT · March 28, 2009

Hello all,

. As soon as I pulled in my driveway she started to lose rpm and died again.

You're gonna love this one.

You have a bad ground strap on your truck.

WTF is he talking about (is what you are thinking right now)

OK...check it out. Trace your grounds on the truck. As soon as you entered your driveway, it killed again...right?? The whole powertrain shifts while driving up a grade. The motor/trans mounts ALLOW a cushion for the shifts...so they remain undetectable to us.

Now...I bet if you were to have your truck running, in PARK, and rock the truck back-and-forth, it would stall out again on you.

CHECK your major grounds on this truck. As an example, the 400-series trucks were famous for a ground strap shearing off, from being flexed so much. That certain strap was located near the firewall, passenger side. So, that is where I'd be inspecting.

OK...as far as the Bank 2 Knock Sensor...go to parts store, and buy some Intake Gaskets, and a Knock Sensor. Remove the intake, and you will find the knock sensor (rear) cavity has collected water, and will be all corroded and white/chalky. Replace the rear knock sensor, dry out the knock sensor cavity, and replace the intake gaskets.

As far as the P0420, go to your local exhaust shop and start pricing out Catalytic Converters.

Keep us posted...and take a pic of the faulty ground and post it up here.

gnsgn1 · March 28, 2009

Hey Super Stealth, I'm willing to try anything at this point. I'll give it a try and post back in a little while. It's snowing right now.

gnsgn1 · March 28, 2009

Ok, I tried checking every ground that I could find. I took them apart and cleaned them til they were all shiney and tried again. She started normally and idled good. I tried shaking the truck while it was running good and nothing changed. Right at about 15 minutes of idling smoothly she starts to miss and dies. It won't restart right away. If I wait about five minutes she'll start and idle fine but it only lasts for a minute or two and she dies again. I'm really stumped. By the way I've been working on my own cars for the past thirty years so I'm not exactly a rookie, but this one is trying my patience. Any other suggestions more than welcome.

98 Z71 SLT · March 28, 2009

The main engine ground on the block is good??

The other main ground, from the rear of the cylinder head to firewall is good, with no chafing?? (This is the one that usually breaks)

Have a fuel pressure gage on it, while it is running. Make sure that fuel is staying where it should. If the fuel pressure suddenly drops, then the truck stalls, then the pump could be the culprit.

Also, have you ever replaced the fuel level sensor in this truck?? Did you get a new level sensor with the replacement pump??

Check 3 more grounds also. 2 grounds are located under the truck...bolted to the frame, under the driver door. 10mm bolts are used to bolt the grounds to the frame. Take them apart, clean the grounds, scuff/sanpaper the area of the frame, then reassemble.

The other ground I'm talking about is near the fuel tank, near the filler neck. Some models have different locations...some on frame, some to the actual neck...but double check this ground is also clean and secure.

Fuel pressure regulator...does it squirt fuel with engine running, vacuum line removed ??

gnsgn1 · March 30, 2009

Update!! It's fixed!!

You guys will never guess what it was and I'm not tellin'. Just kidding, cause this might help somebody with similar problems. It was water in the computer connections! I unplugged the computer on a whim and sure enough there was water and some nasty white corrosion in the blue plug. There are two multi-pin connectors on the computer, one side is blue and the other is red. I only had corrosion on the blue side. I cleaned the pins with a brass brush and contact cleaner, then blew it out with compressed air. I used a little dielectric grease on the connector. I hooked it back up and the truck started on the first try and ran perfectly. I drove for about two hours with no issues. I'm calling it fixed. Hope this helps someone else. Thanks for the help.