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

Is there continuity?

YES | - | Repair short in the wire between the ECM/PCM (A20) and the APP sensor, the EGR valve (K20Z2 engine), the output shaft (countershaft) speed sensor.■
NO | - | Update the ECM/PCM if it does not have the latest software, or subsutitute a known-good, ECM/PCM, then recheck. If the symptom/indication goes away with a known-good ECM/PCM, replace the original ECM / PCM .■