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4 Codes After Head Rebuild


MankDeems3.0

Member
Joined
Nov 29, 2021
Messages
20
City
Fargo ND
Vehicle Year
1999
Transmission
Manual
Alrighty, found my blown fuse in my charging system. now that I can connect to OBDII I have 4 Trouble codes after rebuilding my heads.
P0112 IAT Sen 1 Circuit Low
p0113 IAT Sens 1 Circuit High
P0123 Throttle/pedal c Pos Sens/Switch A Circuit High
P1121 Throttle Pos Sens A Inconsistent With MAF

My initial inclination was my pigtails are backwards but the TPS and IAT are not interchangeable. anyone have any ideas? Truck runs really bad but the rotating assy sounds fine. I've attached my trouble codes below.
 

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Unplug both IAT and TPS
Reset computer/clear codes
Restart engine

See what codes come up

Should be
P0109 Intake Air Temperature Circuit Malfunction
P0120 Throttle/Petal Position Sensor/Switch A Circuit Malfunction

You are testing if there is a short in the wires to these sensors

Ignore
P1121 Throttle Pos Sens A Inconsistent With MAF
Its only there because of the TPS code

Both IAT and TPS share 5v power from computer, so does ECT sensor and MAF but no ECT sensor or MAF codes so "we" can assume both sensor are getting a good reference voltage
But you can test the grey/red wires at each sensor with key on engine off to make sure
Test to battery Negative and ALSO battery positive, its a pull down circuit so can appear as a ground, not 5v but you should see the 5v difference as a +/- 5v
 
Unplug both IAT and TPS
Reset computer/clear codes
Restart engine

See what codes come up

Should be
P0109 Intake Air Temperature Circuit Malfunction
P0120 Throttle/Petal Position Sensor/Switch A Circuit Malfunction

You are testing if there is a short in the wires to these sensors

Ignore
P1121 Throttle Pos Sens A Inconsistent With MAF
Its only there because of the TPS code

Both IAT and TPS share 5v power from computer, so does ECT sensor and MAF but no ECT sensor or MAF codes so "we" can assume both sensor are getting a good reference voltage
But you can test the grey/red wires at each sensor with key on engine off to make sure
Test to battery Negative and ALSO battery positive, its a pull down circuit so can appear as a ground, not 5v but you should see the 5v difference as a +/- 5v

Will test in the AM and see what codes come up. I work at a dealership but diag is still not cheap. What would be the next avenue if there isn't a short in the wire?
 

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