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Chevy Suburban Trouble Code 22

1994 Chevy Suburban C1500 2wd. 5.7 liter throttle body injected. Truck runs pretty good but misses slightly every once in a while at highway speeds.

I checked for codes and there was only one code, a 22 “Throttle Position Sensor Voltage Low”. CEL had never illuminated. I cleared the code, and drove another couple hundred miles, and checked again for the code. Nothing.

I drove yet another 200 miles and checked again for codes, and again saw the 22, even though as nearly as I could tell, again the CEL never illuminated.

I went to and looked up the diagnostic procedure for the code 22. First step was to backprobe terminals A and B (gray and black wires) with key ON to check for 5 constant volts from ECM. Bingo. 5 volts exactly.

Next step was to backprobe TPS wire harness terminals C and B (blue an black wires). Expected result here according to autozone is voltage at closed throttle with key ON should start at about 0.5 volts, and as throttle is opened gradually, voltage should increase smoothly. They do not state what the voltage reading should be at WOT. Anyway, it seemed to check out fine. Voltage went from .5 volts to about 4.5 smoothly from closed throttle to WOT.

I rechecked and reset my probes and restested three times. Same result all three times.

Anyone have any thoughts on how what the problem underlying this code 22 is?

Unfortunately this is an intermittent problem that you wont catch without it acting up. You do however hava a recurring code 22. The majority of the time replacing the tps will fix that. Not in all cases though. Have you disconnected the tps itself and looked for corrosion? You’re right on with the voltages you had by the way. Also you could pull the ecm connectors off and make sure theyre ok.

Thanks. Will check the ecm connections and the TPS itself.