cam sensor fault

[dobsons dyno tune]

Can any one help i have a GMC SIERRA 2500 HD SLE 510 with a repeating fault the diagnostic codes are
P0343 camshaft position sensor (cmp) sensor circuit high
P1781 transmission controll module (tcm) MIL req
Status PC on botH
Module ($10) "Powertrain Control
I have replaced the camshaft sensor with a new one that was in the front of the engine on the camshaft. On the scope the pattern looks good, if i clear the code, it will stay gone untill the next cold start. Before i changed the camshaft sensor the engine would cut out occasionaly at low rpm when cruising, would then back fire bad when cranking to restart. If the vehicle is left for 20 mins it would then restart fine. Since iv replaced the camshaft sensor it hasnt cut out or been hard to start (except cold start)
The truck is also on LPG, the previous fault was worse when running on LPG.
Cheers Ross

[joecar]

Check all the ground connections.

[dobsons dyno tune]

Have done, even ran extra earth, on the scope the signal is earthing to zero

[Bruce Melton]

When I put in my 402 the engine would run as you describe and start badly but then run. Same type of codes. Found the Katech ext cable had reversed sensor connections. Reversed them and all ok.