NHTSA Complaint #11627479 — 2021 CHEVROLET BLAZER

P0128, AC not working, Steering Assist Reduced, and Temp Gauge not working. Problem caused by faulty ECT wiring. First the problem is the ECT is a two wire (signal + and -) 26 gauge wire running through the ignition coil wire harness. Ignition coil signals are very high voltage and fairly fast frequency which causes a lot of EMI which is easily picked up on a 2 wire voltage based wire set. The ECT wiring should have been a twisted shielded pair if running next to Coil wiring or they could have used a single wire resistance thermistor, but they should have just routed the signal a different way to begin with. This is a design issue and it should be a recall...maybe a class action lawsuit is needed to force them to fix it correctly. The FSB (field service bulletin) fix blames loose connector terminals and it patches the computer software to not include ECT wire failures in the Steering, AC, and temp gauge inhibit logic (overtemp readings will still fail off these functions). Also the P0128 code can come back occasionally.