1. Check for continuity between PCM connector terminal A20 and body ground.

Is there continuity?

YES | - | Repair short to ground in the wire between PCM connector terminal A20 and the output shaft (countershaft) speed sensor, then go to Step 30 .
NO | - | Check for loose or poor connections at PCM connector terminal A20. If the connection is OK, update the PCM if it does not have the latest software, or substitute a known-good PCM, then recheck. If the symptom/indication goes away with a known-good PCM, replace the original PCM .■