Symptom: car (98 6MT coupe) started right up, idled OK but had no power. As soon as you started to lift the clutch and accelerate away - immediate stall.

Checking DTC's found the usual slew of body codes from doors not talking properly (like that from new) but one real PCM DTC - P1626. Definition is that the body computer did not send the right password along at start up, hence it thinks the car is being stolen, and cuts fuel but not completely. No check engine warning light, no DIC error display - no nothing.

Read the appropriate manual section, and to clear it you either use the diagnostic tool or interrupt the PCM battery voltage, i.e. disconnect the battery. Then it clicked. A while back I had changed the battery. So, off with the battery terminals (which were tight), and under the +ve cap there was significant corrosion. Not there when I changed the battery a few months back. So, scrape the copper plate and the terminal clean and smear the whole thing with gobs of Vaseline (one of its other uses...), put it all back together and - fixed. I guess there really was not 100% good contact - just enough to screw up comms between the modules.

Btw, new battery is a Sears Platinum, which replaced a circa 2000 Delco. Per Consumer Reports the best battery they ever tested. At it's price, I would hope so. It certainly spins the engine over easily enough in very cold weather even after standing for 3-4 weeks.

Insufficient voltage is the source of many issues with the C5. The best place to start is with the battery, cables, and grounds. Thank you for the tip it could save lots of trouble and money. Most take it to the dealer who changes out modules and parts when the issue could easily be resolved if you know where to look. Great tip, Thanks Rogerd

Fix was solid - car has been fine ever since...