LS1Silverado05

iTrader: (41)

So I checked my CEL and I had the P0121 and P0122 Codes in there.... as well as a P0102 (MAF)....

I have checked the TPS and...

I have a solid verified ground...

I show .58V at idle position...

I see a smooth progression with the throttle sweep...

I show 4.5V at WOT...

Unless Im mistaken this shows that my TPS is fine?

Any advice on where to look next?.. Possibly related to the MAF code?...

JonCR96Z

iTrader: (33)

the p0121 seems possible to be related to the MAF, but the p0122 doesn't.

http://gearchatter.com/viewforum34.p...71e51a3b460f07

LS1Silverado05

iTrader: (41)

Hey nice link! Thanks man.

Well I just probed the MAF a minute ago with key on and..

I show a verified ground

I show 11.5V at the pink wire (11.99 at the battery)..I assume the .5V loss is normal?...

I dont know what I am looking for with the yellow wire but it shows 4.97V

Anymore advice?..

LS1Silverado05

iTrader: (41)

** I should mention that while my checks with my multimeter including the sweep voltage...seemed to check on on the TPS, when it was hooked to a friends scanner the car would show what seemed to be an accurate %throttle under load... but at idle or reving it up it would show accurate... but maybe just because there isnt enough time to register under load?...

LS1Silverado05

iTrader: (41)

bump Man I hope someone has an idea... I dont wanna pay someone to fix this heap.

JonCR96Z

iTrader: (33)

So as measured a the TPS it's fine but the PCM isn't seeing it? Have you done a continuity check on those signal wires back to the PCM?

LS1Silverado05

iTrader: (41)

No..because I was assuming since at the TPS I have the corresponding Voltage I was OK. But you are saying that those wires to the PCM could be an independently bad connection?...

Guess I need to find a 98 Pin diagram and check for cont...

Same deal for MAF I assume? I just posted about my MAF issue as well...

JonCR96Z

iTrader: (33)

Possibly. Anything thing else happen to the car, that could have damaged wires or cause electrical problems?

LS1Silverado05

iTrader: (41)

Well not that I know of, but I just bought the car so I have no idea previous to my owning it. But engine bay appears unmolested..wiring etc.

LS1Silverado05

iTrader: (41)

At the advice of a local tuner/friend. I tapped into the 5V reference wire of both my MAF and my TPS while driving and here were my findings...any thoughts? Normal? see something off? Ideas of where to look next?...

When tapped into the MAF 5V Reference

-Idle= 4.3V
-Part Throttle= 3.6V (fluctuated depending % throttle)
-WOT=2.5V

There was NO random fluctuation...if I drove around light throttle it would steady stay 4.0V or above...as soon as I rolled into it I would see a drop and see anywhere in the mid to high 3V...WOT always dropped into 2.5-2.75 territory...It was certainly correspondent to throttle position...I could control it with the pedal.

When tapped into the TPS 5V Reference

-Idle= 5.0-5.01V
-Part Throttle= 5.02-5.04V
-WOT=5.08V

Unlike the MAF findings...the TPS NEVER dropped below 5.0V...and in fact when given throttle it slightly increased...

LS1Silverado05

iTrader: (41)

For everyone's reference. I think I may have found my issue. I noticed the air pump really dimmed my headlights the other night when it came on, and I said to myself... "man, I wonder if that is pulling enough juice to be throwing my low signal codes?"...

So I pulled the air pump relay and fuse, and it looks like now that a few ignition cycles have occured, I only have air pump codes now..no more P0102 or P0121 ... Keeping my fingers crossed that it stays off.

MaroMan

iTrader: (6)

I know its old but im having the same problem, any update for us p0121 code people?