I have been having some issues lately with my Lightning... before anyone asks if I've done a tune up lately, yes. I keep getting a Check Engine light with codes 121 and 212.. 121 is for Low-Voltage from the TPS if I'm not mistaken, so I grabbed a multimeter and started testing away. First I tested the Voltage Reference wire (Redish-Orange) to make sure I had 5 volts, and it came out at 5.07 volts. Secondly I tested the Signal Return ground wire (Green) to check for 10-12 volts, which came up at 13.something.. I tested it by running the red probe to the positive terminal on the battery and checking the green wire with the black probe. Last I checked the TP Signal wire (Black) for .96-.98 volts.. all I got was .03 volts... I checked all three wires by back probing the connector on the sensor side of the connection, so I know it's not a connector problem, and my TPS is a BRAND NEW Borg-Warner so I wouldn't think there's a problem with it.. If anyone wants to dive into the 212 (Loss of diagnostic monitoring.. SPOUT to ground) code go ahead but I think that's a separate matter. But I really need help.. this truck is driving me up the wall. Thanks for any and all input! -Aaron

 

Set your meter to continuity, unplug the TPS and compare the signal pin to ground. If you get continuity, I'd suspect a short to ground in the harness somewhere.

Edit: You messed up. Green is the TPS signal wire, black is ground.