Car will not start 2008 Pontiac Grand Prix V6 135,000 miles
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. Removed and replaced 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 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. Battery is good, lights, horn etc. But no activity from starter. Any thoughts are appreciated.