JamesSam's TBI Code 21 Test Thread

[JamesSam]

@gmbellew and @AuroraGirl
Starting this so pics can be posted. Some of the preceding events I have discussed due to my truck going back and forth between driving great and not great at all. Most recently I did the paper clip OBDI adjust and set IACV needle and adjusted the idle screw(probably shouldn't have).
The truck went from running terrible to great, but the service engine light stayed on even though running smoothly.

Checking OBD1 codes with the paper clip scanner trick it sent back code 21: Throttle Position Sensor signal voltage high. After this it eventually went from good idle to high idle abruptly while warming up and driving not so well again. I got a voltmeter finally and tested the aftermarket TPS and a new AC Delco TPS.
Aftermarket closed and WOT:

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New TPS closed and WOT

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[JamesSam]

New AC Delco TPS is installed on the truck. Closed and WOT:

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Where do I go next? Fire it up or readjust some stuff in OBD1 with paper clip jump?

 

[Ricko1966]

Just,to clarify,so others don't read this and think these trucks are OBD1 they are not OBD1 they are a proprietary system of GMs edit.the reason I said anything is people read OBD1 and.immediately assume they can buy an obd1.scanner and be good to go. But they can't. They need a tech.1 or Snap on redbrick,I think otc Genesis works to but not your generic obd1 stuff.

 

[JamesSam]

Just,to clarify,so others don't read this and think these trucks are OBD1 they are not OBD1 they are a proprietary system of GMs

No offense others. When I say OBD1 I am referring to the proprietary to GM system that is similar.

 

[JamesSam]

Just,to clarify,so others don't read this and think these trucks are OBD1 they are not OBD1 they are a proprietary system of GMs edit.the reason I said anything is people read OBD1 and.immediately assume they can buy an obd1.scanner and be good to go. But they can't. They need a tech.1 or Snap on redbrick,I think otc Genesis works to but not your generic obd1 stuff.

Also news to me. Thanks for the info @Ricko1966 . I'm glad I haven't tried to invest in a generic OBD1 scanner. So far just using a paper clip.

 

[77Dmax]

Check the range, not just idle and WOT.

 

[JamesSam]

Check the range, not just idle and WOT.

It seemed to flow from closed to open with no interuptions in between on the new TPS.

 

[gmbellew]

id say fire it up and run it with the new TPS.

 

[77Dmax]

Idle voltage should be a bit lower. I think the spec is .40-.50. If you are unable to achieve that you probably adjusted the idle screw too high. The IAC should be able to compensate for the adjustment.

Also it's good practice to use the computer ground for your DVOM when reading voltage off these sensors. You'll get a reading that is more in line with what the ecm is seeing. It's also a good way to make sure the ecm is grounded properly- the numbers shouldn't change between using the battery as a ground or the ground the sensor is using. Poor grounds on these systems will cause voltage spikes through sensors due to ground searching. Of course making sure the grounds are clean should be one of the first things you do.

 

[Sgt Gus]

Watching...perseverance Brother!

 

[JamesSam]

After work today, while the better half and the kids were at the pool, I thought about what exactly I should do 1st, 2nd, and last with the new TPS installed. Then I decided I was just gonna crank it up.
It took about 2 seconds to turn over but once it did, it ignited quickly and powerfully. Once it was warmed up it was sounding great and the service engine light was cleared. I drove it to the store for groceries and it was good with the exception of two moments when it felt like it wasn't...after a couple more drives and offs and ons, it was firing right up and driving well.
I am planning to drive it to work tomorrow (18 mile round trip) for a real test drive.