Story: Faulty Coolant Sensor Generates Faulty Error Codes.
 

- I would like to share an interesting experience that I witnessed yesterday to all S80 owners. Some of the car terminology I use might incorrect but I will try to describe them as much as possible.

- I visited my trusty mechanic/shop owner yesterday and his wife 2000 S80 (T6) Volvo was in the shop for repair. The message display in the car indicated that: a) Low coolant level; b) Transmission requires service; c) Stop Engine. He can shift the car in to Drive, but the engine would die once the gas pedal is pressed. Semi-manual shifter (up and down gear manually by push up or down on the shifter) would not engage – no gear indicator display of which gear you are currently and the car wouldn’t move.

- He used the scanner (I don’t remember the name but it has a very large multi-line color touch screen LCD display) and the scanner indicated that: a) Coolant sensor is faulty; b) Something about transmission control module (the left silver large module in the compartment in front of the coolant overflow tank; the right one next to it is for control the engine) faulty configuration; c) Transmission is faulty.

- First he assume that his wife probably break the transmission (his is not too surprise of the way she drives) so he tackle the big problem first by replace the transmission control module thing (TCM for short) by replace it with a working spare one and reset everything to see if it would clear some of the codes related to the transmission. But any way, still no go with the same bunch of error codes.

- So after a few beers and a lot of swearing at Volvo; he put the old TCM back and replaced the old coolant over flow tank (I believe the sensor is built-in) with a new one. Finally, everything start up with not a single error code; the car run as normal.


Why such a simple thing as a faulty coolant sensor can generate all kind of unrelated error codes? Especially it relates to something major and expensive as the transmission. What happen if this happen to our car and we take it to a dealer and obviously, they going to follow the diagnostic outputs and recommend to replace the TCM or worse, the transmission? So basically we gonna empty our wallet for nothing !!!