2008 Grand Prix V6 135,000 miles

[smoraq]

Saturday Mechanic Needs advice please
Coolant was leaking into unknown area of engine, no white exhaust, no milky oil. Replaced about 2 quarts of water every 4 days or so. Last week I removed and replaced manifolds both Lower and Upper (plenum) gaskets. Installed new thermostat, refilled with new Dex-coolant, bled system. Engine ran fine for several days. No coolant leaks. Then yesterday the Engine light came on and codes P2138 and P1125 appeared on code scanner. Seems to direct to Throttle Position sensor. I am concerned that wires (harness) to TPS might have become frayed while wrestling to remove and replace both manifolds. At any rate, car just died at intersection. Turning key results in no activity from starter. Battery is good, lights, horn etc. But no activity from starter. Any thoughts are appreciated.

[MikeCStig]

Originally Posted by smoraq

I am concerned that wires (harness) to TPS might have become frayed while wrestling to remove and replace both manifolds.

That sounds about right. The connectors on some sensors (especially on pre-bailout GM cars) can be pretty flimsy. I would start by checking the wires and connections you had to disconnect and other connections in surrounding areas. I can't really imagine the sensors themselves going bad just because you did the manifold gaskets, but I guess it's possible.

[smoraq]

Thanks very much. So you think a bad wire to a sensor could cause no power to starter?

[MikeCStig]

It could be a bad connection triggering a lockout and disabling the starter.

[smoraq]

Interesting, thank you again. If that's the case, can you advise how to get starter operational again.

[MikeCStig]

If I found that sort of problem, I'd probably just re wire the problem area.