PCM Diagnostics & Tuning HP Tuners | Holley | Diablo

P0122 code

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Old Nov 3, 2009 | 05:42 PM
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Default P0122 code

Working on my brother's 68 camaro with a 01 camaro ECU and harness (05 Caddy ESV block and 243 heads)

Yesterday we cleaned up the battery ground point from the battery to the body (relocated battery to trunk) At the same time, I also installed a set of truck coils.

Since then the car doesnt run correctly as it did before, it sorta holds the idle or hunts for it, just like if the TPS sensor was bad. Pulled the codes and have a P0122 for the TPS. Checking the sensor, it all appears to be working correctly, getting the 5v ref, good ground, and good sweeping voltage when throttle is opened. But the p0122 will not clear.

Any Ideas?
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Old Nov 4, 2009 | 05:26 AM
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This code is set when voltage goes below .2V for more than 10 seconds.

Check your voltage with the throttle closed. It could still be a bad sensor, or it's out of adjustment.

Could also be an intermittent wiring problem. Maybe something was disturbed when you changed the coils?

Just a few ideas.

Ideally, you want closed throttle to be about .6V, and WOT to be 4.6V.
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Old Nov 4, 2009 | 06:17 AM
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Actually .45-.55 volts. The PCM tries to enter a different table if the voltage is not in this range.

If that is all you did, try the following.

You may need to do a idle relearn procedure. Sometimes when the battery is disconnected for an extended period of time, the PCM needs to relearn the TPS and IAC positions.

Turn the key off, engine off.
Unplug the TPS connector and IAC.
Turn the key on, engine off.
This will set the TPS and IAC codes.
Turn key off, reconnect TPS and IAC.
Start engine. The idle may hunt for a few minutes until it knows the air flow requirements and then stabilizes.
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Old Nov 4, 2009 | 09:08 AM
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I will do the relearn first, then try to reset the TPS position and get back to yall. Thanks for the imput
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Old Nov 4, 2009 | 02:22 PM
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also, when the scanner is connected to the computer, and the car is running.. The Ignition Voltage reading is at 13.8 at idle but when you raise the RPM's up it drops down, the lowest reading was 6.5v. My GTO doesnt do this it stays at 13.8 thru the entire RPM range, what could cause this?
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Old Nov 4, 2009 | 02:28 PM
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Sounds like ground issues.
Where is the battery ground connected? I have a first gen Firebird, battery in trunk also.

Big heavy cables or braided ground straps
Ground from the engine to the subframe.
Ground from the subframe to the body.

Plus the normal engine grounds on the drivers rear of cylinder head.
Drivers front lower block.
Front of passenger side cylinder head.
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