dirty ground signal help!!
Thread Starter
Teching In
Joined: Jul 2016
Posts: 26
Likes: 2
dirty ground signal help!! I have 5.3/4l60e from a 2000 gmc sierra swapped in a 99 jeep wrangler. been working with black bear performance on the tune using a auto cal for data logging. the issue im having is its like its hitting the rev limiter when I go full throttle. sometimes it will run on out like normal but not that often, most of the time I have to get on and off the throttle for it to finally clear up. sometimes it will run up hit the limiter and die. tuner said he thought it could be the crank position sensor but I changed it with a delco sensor around 8 months before going with the tuner and with the new sensor nothing changed. I told the tuner and he suggested a dirty ground signal. I have made new 2 gauge battery cables from the battery to the block, the block to the alternator bracket and from there to the firewall and no change to the way it runs. latest update he got my cold start pretty good and said digging through the old logs it really looks like a dirty ground or something like that. both the vehicle speed and engine tachometer signals are dirty. novak conversions did my harness and im not sure how the grounds are ran but 1 ground goes to the block. im not sure if the are looped or whatever but im ready to burn the motor down. not sure where to go from here...any suggestions?
TECH Fanatic
Joined: Dec 2017
Posts: 1,467
Likes: 265
From: Bossier City, Louisiana
They are black wires with a small white stripe on the harness for my 1999 GMC Sierra 5.3 liter engine's PCM - in a 1970 Chevy El Camino. Its pins 1 and 40 on the PCM blue connector and pins 1 and 40 on the PCM red connector. There are other grounds for individual sensors but these four seem to the most important . . . . direct ground lines to the PCM. My harness has them grounded to two different places but if you are concerned, tie them all together in your harness and extend the wires temporarily all the way to the negative post on the battery. If your problem goes away, you know you need to work on the grounding half of your electrical system. You could also have a broken wire on one of these pins and a continuity check with a good multimeter might reveal it.
Rick
Rick
It's a moot point if someone has modified the harness, because you never know if they've combined all the grounds together. You would need to contact the people who did the harness to find out.
You dont by chance have anything spliced into the VSS wires do you? Auto meter says to splice into them for their speedometer, but when I did that it messed with the signal going to the PCM enough that it would act like what you are describing. Also messed with the shifting of the transmission.
You dont by chance have anything spliced into the VSS wires do you? Auto meter says to splice into them for their speedometer, but when I did that it messed with the signal going to the PCM enough that it would act like what you are describing. Also messed with the shifting of the transmission.
Thread Starter
Teching In
Joined: Jul 2016
Posts: 26
Likes: 2
It's a moot point if someone has modified the harness, because you never know if they've combined all the grounds together. You would need to contact the people who did the harness to find out.
You dont by chance have anything spliced into the VSS wires do you? Auto meter says to splice into them for their speedometer, but when I did that it messed with the signal going to the PCM enough that it would act like what you are describing. Also messed with the shifting of the transmission.
You dont by chance have anything spliced into the VSS wires do you? Auto meter says to splice into them for their speedometer, but when I did that it messed with the signal going to the PCM enough that it would act like what you are describing. Also messed with the shifting of the transmission.
Trending Topics
Thread Starter
Teching In
Joined: Jul 2016
Posts: 26
Likes: 2
actually nova ill have to check tomorrow to see if I spliced in the the vss wire or not, I called novak when I was doing the wiring and I believe they sent me a pin to plug in to pin 50 on the red connector so I didn't have to splice in to the vss because I had read about the interference. its been atleast a year and a half since I done all the wiring.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo Thread Starter
Teching In
Joined: Jul 2016
Posts: 26
Likes: 2
I didnt splice in the vss wires I came out of the computer on pin 50 vehicle speed output circuit 4k to the wire from the speedometer. I had a resistor between that wire and the pink wire to boost the signal to the speedometer according to the gauge wiring. I removed that resistor where nothing was tied to it and it seemed like it cleared up a little bit but still does it. On my way to work this morning I got full throttle several times and it threw a code of po336 crankshaft position sensor, it has never thrown a code before.