VR 5.0L Code 22 Recurring

[Dean1985]

Hey guys.

I have used the good old search function, gone through 5 pages of posts (165 results) and cant really see anyone with an answer to an issue im having.

I have had a recurring code 22. TPS return voltage low.
I have a healthy 5v reference voltage, i have tested the retyrn voltage back to the ecu which is between .4 of a volt at butterfly idle. The voltage gently increases back to 4.2v or a little more at full throttle with no spikes etc.

After a drive (maybe 5 minutes or more) the engine light will come on and the PCM will later report code 22 again.

I have replaced the TPS. Borrowed a throttle body with sensors in it as well. Tested all 3 TPS which were all within spec. But after the specified driving time... bad shifting, loss of gears. Engine light.
My brirher is a mech so we have also had it on the snap-on scan tool running through fault finding steps and evwrything check out.

Until, it throws the code. When the code is present we test the TPS and the voltage doesnt increase until just under 50% throttle.

The wiring harness has been stripped back to where it meets the guard to check for wiring issues. To no avail.
I had an earth issue at the passenger head earth which i moved and fixed.

I have good earth from battery to guard. Engine to battery, engine to body. The one near the oil pressure switch looks a bit shitty but i doubt itd be an issue.

Any thoughts?

Cheers in advance

 

[Immortality]

What is the reference voltage when the fault occurs? Borrow a different PCM and test.

 

[delcowizzid]

Closed throttle it should be around 0.4v and no higher than 0.55 and it shouldn't change. The ecu reads the tps volts at key on and auto zeros it if its stuck partly open and then sucks closed once running can cause you grief so can other things like low vacum readings on the map sensor can trigger tps codes

 

[Dean1985]

I was having the issue prior to the cam swap.
I was on my way to Sydney, cruizing along the freeway and then felt a surge... then it kept going... then felt a series of surges and pulled over. The car was running rough and then cleared up.

I took off and then it wouldnt change gears... and you know the rest from there.

Since then (due to cylinder pressure/detonation issues) i have simce changed to a Cran 284 cam.

As it should, the issue has persisted and that has been my time and investigation woe since then.

 

[Dean1985]

Closed throttle it should be around 0.4v and no higher than 0.55 and it shouldn't change. The ecu reads the tps volts at key on and auto zeros it if its stuck partly open and then sucks closed once running can cause you grief so can other things like low vacum readings on the map sensor can trigger tps codes

Hey mate. Checked the values again. Was going off memory. I have changed OP to reflect values taken.

 

[Dean1985]

What is the reference voltage when the fault occurs? Borrow a different PCM and test.

Let me get back to you on that. Good question, thank you.
I didnt take much notice, i seen it was wrong and played around with it then swapped the throttle body thinking it would fix it.

 

[gtrboyy]

Earths in engine to ecu harness all linked together tps/map/o2 etc

When did v8 conversion had few weird codes come up like map sensor,tps once or twice....strayed earth wire at rear of head + extra unneeded terminal plugs/wires solved most of it & went to trouble of sanding head/thinners for bare & clean metal contact.

No more codes but did that occasional surge thing too & rich smell/cold starts so decided to replace cts although while there took earth off at front of engine cleaned oil/paint/gunk off terminal/bolt/mating surfaces..not surged since then but still think it was earth issue all along

 

[Dean1985]

Well. After a run and a bit of messing around i came up with some more info.

Gtrboy; its probably something to do with earthing. So Kudos.

Went for a drive.the thing shifted amazingly. Drove well.
Went down a hill and wwnt to do a uturn and the engine light came on and she nearly stalled. I thought maybe it was a rich cide from coasting with this cam plunking buckets of raw fuel out the arse due to specs.

Car made it up the hill and i gave her a bit of throttle and shifted fine and the engine light went away.. all matched up to be a potential rich burn code.

Got home and checked the codes. Tps. Low voltage.

So the checks began. On the return wire to the pcm i had .8v. We all know thats too high.

So we started checking around.
*Checked alt charge: 13v. - Bit lazy at idle. Up to 14.7v at 2k rpm
*Checked loss between alt and battery on the charge cable: .2v voltage drop
*We began checking earths (dont ask methodology) but were looking to see they had continuity to the battery: all good

I put neg of the multimeter on the battery and pos on the radiator and got .4v......

I ran an earth lead from the battery to the radiator and it went away.
I couldnt believe it.
I turned the meter off. Zerod the meter and tried again with the car off. Now showing -.4v

Is it possible that when the car starts its zeroing the tps to its pre start return signal. .4v at times. And then when driving the voltage drops to .0 due to this leak?

 

[gtrboyy]

When doing conversions I used to add earths just to avoid weird issues later on.Sometimes fix is obvious other times just a fluke.

The cars are old now with lots of heat cycles,oil leaks etc so no surprise wiring gets brittle or damaged for various reasons or even loose/dirty connections.

My vp v8 ute rips hard bang for bucks wise..runs well & everything checks out 100% yet to me still feels like it has weakish spark although starting to think it's more heatsoak or heat control issue with how hot engines bays get in these things.

Always going to be looking at things to fix or improve on our cars lol

 

[Immortality]

Definitely don't want an earth current leak through the cooling system as that will cause electrolysis and eat up alloy parts like the radiator. This is why the radiator is rubber mounted to isolate it from the chassis.

Clean and tighten all earths on the block, battery and chassis. Personally I like to add an extra earth cable from the alternator body directly to the battery negative. The alternator is the source of all power on your car, you have a big red cable going from the alternator directly to the battery but the earth system has to pass via mechanical connections where the alternator is bolted to the head via brackets, from the head to the block and from the block via cable to the battery....