CEM cannot be diagnosed

Juozys · Jun 7th, 2019, 11:58

Hello,

Im having a headache from trying to find out why CEM is not diagnosing on Volvo XC90. All blocks on LS CAN are diagnosing fine, except SRS module, but CAN seem to pass through it just fine. On the other hand everything on HS CAN is not diagnosing at all . Ive read numerous manuals about CAN network in these cars and ive read that LS CAN resistors is located in UEM and REM, both 120ohm. HS CAN resistors are in ECM and ABS both also 120 ohms. So in obd2 port measuring resistance on LS and HS can pins should show 60ohms, and if there is open circuit it should show 120ohms. So my question is does both CAN resistors must be pluged in into network in order for HS network to work at all? But on the other hand when i disconect REM i get 120ohm on obd2 pins as if there is open circuit, but everything else on LS CAN is diagnosing anyway. So it kind of denies my question 😀 but just to make sure, maybe there is something different about HS CAN?

P.s. All the experimenting was done with a new, guaranteed working CEM. I also tried disconecting modules on HS one by one to see maybe some of them is giving problems for the network.

Thanks in advance!

Jun 7th, 2019, 11:58	#1
Juozys New Member Last Online: Nov 7th, 2023 07:38 Join Date: May 2019 Location: Kaunas	CEM cannot be diagnosed Hello, Im having a headache from trying to find out why CEM is not diagnosing on Volvo XC90. All blocks on LS CAN are diagnosing fine, except SRS module, but CAN seem to pass through it just fine. On the other hand everything on HS CAN is not diagnosing at all . Ive read numerous manuals about CAN network in these cars and ive read that LS CAN resistors is located in UEM and REM, both 120ohm. HS CAN resistors are in ECM and ABS both also 120 ohms. So in obd2 port measuring resistance on LS and HS can pins should show 60ohms, and if there is open circuit it should show 120ohms. So my question is does both CAN resistors must be pluged in into network in order for HS network to work at all? But on the other hand when i disconect REM i get 120ohm on obd2 pins as if there is open circuit, but everything else on LS CAN is diagnosing anyway. So it kind of denies my question 😀 but just to make sure, maybe there is something different about HS CAN? P.s. All the experimenting was done with a new, guaranteed working CEM. I also tried disconecting modules on HS one by one to see maybe some of them is giving problems for the network. Thanks in advance!

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