2002 SAAB 9-5 Engine light is on

JDMONAC

MEMBER
2002 SAAB 9-5
4 CYL
2WD
AUTOMATIC
132,000 MILES

My engine light is on, my mechanic is stumbled so I don't know what to do, the code reads P0116 which is the cooling system, he replaced the thermostat, and the sensor and the coolant level is perfectly fine, any suggestions, he tried resetting it but the same code still comes on

1 Reply

FACTORYJACK

MECHANIC
4,159 POSTS

If the sensor was replaced, and the code still sets, it is a circuit fault or a faulty ECM. Ideally, you would need a scan tool to read what the temp value is. It is a two wire sensor hard wired to the ecm. I am showing that pin one at the sensor should be 5V, and pin 2 is grounded by the ECM, the measured voltage drop would be calculated into temperature internally. You could check for 5V at pin one of the sensor connector, and for continuity to ground at pin 2. This would develop a diagnostic process. If you were missing 5V, then backprobe pin 39 at the ECM and check for 5V there. If you have it there, then you have a wiring fault, if not you may have a module fault. Same for the ground side, if you have no continuity to ground at the sensor connector, backprobe pin 22, if or if not, same scenario.