no power to tps 5v reference from pcm

Hello
I have a 2000 Silverado 4x4 with the 5.3l v8.

Warning it may be a little confusing!

The tps or throttle position sensor uses a 5v reference from the pcm or powertrain control module. My tps is only getting 1.27 volts. I have checked the feed wire at the pcm and am getting the same 1.27v. This led me to believe the pcm was bad. The wire between the pcm and tps was tested and doesnt have a break or short to ground. So I bought a used pcm and installed it. Again i got 1.27v. Im stumped. I have talked to my local chev dealer and they tell me its either the tps, wiring or the pcm. I have replaced the pcm and tps and still no luck. I could understand if the pcm was sending 5v but only 1.27v was making it to the tps....(bad wire) but if the new pcm is sending the same voltage at the connetor to the harness im stumped. I have checked the connector and it appears to be clean and giving a good connection. I highly doubt i have two bad pcm's so im not sure what else to check. I have $600 and 2 weeks into this problem. If ANYONE has any ideas or has had this problem before please help. The truck runs like crap with no tps and its driving me nuts.

Thanks

Tony

Hello
I have a 2000 Silverado 4x4 with the 5.3l v8.

Warning it may be a little confusing!

The tps or throttle position sensor uses a 5v reference from the pcm or powertrain control module. My tps is only getting 1.27 volts. I have checked the feed wire at the pcm and am getting the same 1.27v. This led me to believe the pcm was bad. The wire between the pcm and tps was tested and doesnt have a break or short to ground. So I bought a used pcm and installed it. Again i got 1.27v. Im stumped. I have talked to my local chev dealer and they tell me its either the tps, wiring or the pcm. I have replaced the pcm and tps and still no luck. I could understand if the pcm was sending 5v but only 1.27v was making it to the tps....(bad wire) but if the new pcm is sending the same voltage at the connetor to the harness im stumped. I have checked the connector and it appears to be clean and giving a good connection. I highly doubt i have two bad pcm's so im not sure what else to check. I have $600 and 2 weeks into this problem. If ANYONE has any ideas or has had this problem before please help. The truck runs like crap with no tps and its driving me nuts.

Thanks

Tony


since you have the same vehicle I have I would like to know how this is corrected...

the 5volt reference is the gray wire the black wire is the ground..if the voltage is low here it is most likely that the feed to /from the PCM to the fuel pressure sensor is shorted or sensor defective...

also the DTC will help locate possibly where these problems may be,,

dtc p0122........the dark blue wire at the TPS to the black should be .6volts at idle....4 volts at WOT....

So is the tank pressure sensor wired into the same 5v reference as the tps? Which wires are they going into the tank. I haven't been able to find any info on the tank pressure sensor in my haynes manual. The only dtc im getting are p01639 p0122 and p0121.
Thanks
Tony

So is the tank pressure sensor wired into the same 5v reference as the tps? Which wires are they going into the tank. I haven't been able to find any info on the tank pressure sensor in my haynes manual. The only dtc im getting are p01639 p0122 and p0121.
Thanks
Tony

yes the TPS/FUEL TANK PRESSURE SENSOR use the same 5volt reference voltage. the dtc P1639 means the 5 volt is out of range,,,,

you must find out why ...the wire to the fuel tank may be damaged or the sensor connector to tank,, locate the fuel tank sensor , this may be defective also...

the wire color is gray...pcm C1-45 this goes to the fuel tank sensor...

the 3 wire connector at the fuel tank where the fuel pump is supported is where the FTSENSOR IS MOUNTED...just remove the connector to it and see if the problem goes away [you now have 5 volts..]
if the problem still remains then the wire must be shorted out somewhere..

if the sensor has shorted,, the tank may have to be dropped to get access to replace the sensor,,sensor locked in by retainer clip...

Alright I replaced the Fuel Tank Pressure Sensor with a used one I had on an old fuel sending unit and the truck works perfect. Thanks for all the help!

Tony

Alright I replaced the Fuel Tank Pressure Sensor with a used one I had on an old fuel sending unit and the truck works perfect. Thanks for all the help!

Tony

that sensor must be shorted out ....thanks for that info ...