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Ask Juan Crespo Your Own Question
Juan Crespo
Juan Crespo, Tech Trainer
Category: GMC
Satisfied Customers: 1523
Experience:  A.S.E. Master Technician, Advanced Level, Emissions - Asian, Domestic, & European
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I have a 2001 Yukon 5.3L with error code P1120. Replaced the

Customer Question

I have a 2001 Yukon 5.3L with error code P1120. Replaced the TPS sensor already and it is still throwing this code. Checking wires/connector now - any other suggestions?
Submitted: 1 year ago.
Category: GMC
Expert:  Juan Crespo replied 1 year ago.
Hi there. Welcome to our site. Most tests for this type of code require the use of a scan tool capable of reading engine data (sensor values and voltages) and a digital multimeter to determine whether the issue is related to faulty connector/wiring or bad component. Do you have access to such tools?
Customer: replied 1 year ago.
I have a digital multimeter, but not the scan tool. I brought it by a shop with a scan tool to pull the error code.
Expert:  Juan Crespo replied 1 year ago.
Codes don't necessarily mean a component is bad, instead they are just a way for the OBD-II computer to alert you that a particular circuit has fallen outside the pre-programmed parameters. In this particular case, code P1120 means the computer is detecting a signal from the TP that is going intermittently higher than the pre-programmed high parameter value of 4.9 volts.Does your engine have the optional Electronic Throttle Control (a.k.a. "drive-by-wire"), or the standard throttle body?
Customer: replied 1 year ago.
Yes, a 5.3L with ETC and traction control (which apparently changes the wire/pin out of the TPS). I'm going to measure the voltage on the TPS wiring today. If that checks out what else should I look for?
Expert:  Juan Crespo replied 1 year ago.
OK. Remember you're looking for a condition where the 5V reference signal is intermittently getting shorted to 12V power; look carefully at the connectors, wiggle the harness as you're measuring voltage. Look for any spot in the harness where wires might be chafed and touching one another. Unplug the PCM and look for any signs of water intrusion - spray WD40 on both sides of all connections. Best Regards.