R50/53 Is my ECU toast?
#1
04-22-2023, 11:38 PM
Is my ECU toast?
Sort of a side bar to my CAN Bus problem thread.
Should I be measuring the 120 Ohm CAN bus trunk line termination resistor inside the ECU if I directly measure resistance on pins 29 and 30 (CAN HI and CAN LOW) of the EMS2000 (ECU) in the engine bay?
I'm reading 2.8 Mega Ohms.as shown here https://www.northamericanmotoring.co...ml#post4650336
Thx!
Should I be measuring the 120 Ohm CAN bus trunk line termination resistor inside the ECU if I directly measure resistance on pins 29 and 30 (CAN HI and CAN LOW) of the EMS2000 (ECU) in the engine bay?
I'm reading 2.8 Mega Ohms.as shown here https://www.northamericanmotoring.co...ml#post4650336
Thx!
#3
04-28-2023, 01:25 PM
You need to measure the resistance on the vehicle's wire harness, not on the ECU. Also check for shorts to ground on both wires.
If the resistance checks out then it could be one faulty module creating signal noise on the lines which throws errors on all the modules on the CAN (fairly common cause of CAN issues). To check this, unplug one module at a time, turn car on again and try to clear the codes. If you can't clear any codes, plug module back in, and move on to the next. Repeat until at least some of the codes can be cleared and you found your faulty module that's causing the errors.
Fortunately, there's only a handful of modules in these cars that are on the CAN - Engine, transmission, instrument cluster, ABS/DSC, and the steering angle sensor (only if you have DSC).
If you're a real nerd and own an oscilloscope, you can examine the signal to get a better idea of what's going on.
If the resistance checks out then it could be one faulty module creating signal noise on the lines which throws errors on all the modules on the CAN (fairly common cause of CAN issues). To check this, unplug one module at a time, turn car on again and try to clear the codes. If you can't clear any codes, plug module back in, and move on to the next. Repeat until at least some of the codes can be cleared and you found your faulty module that's causing the errors.
Fortunately, there's only a handful of modules in these cars that are on the CAN - Engine, transmission, instrument cluster, ABS/DSC, and the steering angle sensor (only if you have DSC).
If you're a real nerd and own an oscilloscope, you can examine the signal to get a better idea of what's going on.
#4
04-28-2023, 10:29 PM
You need to measure the resistance on the vehicle's wire harness, not on the ECU. Also check for shorts to ground on both wires.
If the resistance checks out then it could be one faulty module creating signal noise on the lines which throws errors on all the modules on the CAN (fairly common cause of CAN issues). To check this, unplug one module at a time, turn car on again and try to clear the codes. If you can't clear any codes, plug module back in, and move on to the next. Repeat until at least some of the codes can be cleared and you found your faulty module that's causing the errors.
Fortunately, there's only a handful of modules in these cars that are on the CAN - Engine, transmission, instrument cluster, ABS/DSC, and the steering angle sensor (only if you have DSC).
If you're a real nerd and own an oscilloscope, you can examine the signal to get a better idea of what's going on.
If the resistance checks out then it could be one faulty module creating signal noise on the lines which throws errors on all the modules on the CAN (fairly common cause of CAN issues). To check this, unplug one module at a time, turn car on again and try to clear the codes. If you can't clear any codes, plug module back in, and move on to the next. Repeat until at least some of the codes can be cleared and you found your faulty module that's causing the errors.
Fortunately, there's only a handful of modules in these cars that are on the CAN - Engine, transmission, instrument cluster, ABS/DSC, and the steering angle sensor (only if you have DSC).
If you're a real nerd and own an oscilloscope, you can examine the signal to get a better idea of what's going on.
That was my big question here, should I see that 120 Ohm resistance on pins 29 to 30 (CAN Hi / Low) measuring directly into the ECU connector.
Well, I received my refurbished ECU today and measured it before I installed it.
Yes, it does measure the 120 Ohms. So, if you’re not measuring 120 Ohms across pins 29 and 30 of ECU then the CAN bus port on your ECU has failed.
I put the ECU in and all errors cleared up including the dreaded EP “Emergency Program” mode of 6sp Auto transmission. R53 is happy again!
#5
04-29-2023, 02:00 PM
4th Gear
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