Resolving the Hot Start Issue - Replacing the Crankshaft Position Sensor (CPS) 9177221.
Symptoms of a Hot Start Issue are when the car continuously cranks and refuses after a journey when the car gets to operating temperature, however, once cooled it is fine to crank and fire up.
When the ignition is switched on, the Trionic 7 EMS lights the CHECK ENGINE lamp and performs the function check. The fuel pump is activated for 1 second to build the fuel pressure, after which the EMS will await pulses from the Crankshaft Position Sensor, if this fails the EMS will disable the ignition and fuel injection. When the CPS Ohms resistance falls outside the operating perimeters, it activates the failsafe, according to WIS, the Sensor resistance should be 860±90 ohms.
My Saab 9-5 Aero 2.3 Turbo B235R had a hot start issue during the summer of 2020, where, if I switch off the engine when at optimum temperature and attempt to restart within a short timeframe, the car will crank and refuse to fire, however, if I let it rest for 45-60mins it was quite all right.
This was an intermittent issue and I experienced it no more than on three occasions, however, before it got worse I decided to replace the CPS in July with an aftermarket item as I was unable to source a Bosch part.
After replacing the sensor I never had any issues, I am very sure that the heat from the Turbo and CAT destroyed the CPS due to the close proximity to heat. The metal heatshield surrounding the CPS most probably has minimal impact on dispersing or deflecting the heat.
All you will need to replace the CPS is a T30 Torx for the CPS bolt a flat-head screwdriver to remove the wiring loom and a lot of patience.
Tightening torque, nut, and heat shield:
20 Nm (15 lbf ft) (up to and including engine no. 7011078)
21 Nm (16 lbf ft) (from and including engine no. 7011079)
6 сен 2024
