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Tbh i have a done a temp job just to see if it works i chopped my connector off and wired it to the one i bought which had some wiring attached to it
It was just the first clip which was the damaged on the x30/18 the one with the earth connection
Terminal 15 is not a single spot, it is all power available with ignition on. When using the key, this voltage originates at the EIS (ignition switch) and is then distributed to every module and component that uses it. The power to the EIS comes through the front prefuse, so that is the first place to go if the EIS is not being supplied with power. The fuse and relay box diagram shows power coming from the EIS, N73, pins 1 and 2. The feed from the front prefuse enters the EIS at pins 3 and 4. In other words, pins 3 & 4 should always have battery voltage, pins 1 (15) & 2 (15R) are the switched lines and depend on key position.
If you look at the fuses in post 31, they will all have a 15, 15R, or 30 next to them. Terminal 30 is battery power, so these fuses should have power all the time. Terminal 15R is accessory power, the first click of the key or one press on the keyless go button WITHOUT your foot on the brake. Terminal 15 is the second position on the key or 2 presses on the keyless go button without your foot on the brake pedal. It is also active when the key is in the start position or you press the keyless go button with your foot on the brake pedal to start the car.
When using keyless go, the EIS is bypassed. Terminal 15 power for the entire car is provided by relay B and terminal 15R power is provided by relay C. I don't know if you have keyless go, but sometimes a car will work fine with the key but not keyless go and vice versa. This is because terminal 15 power can be provided two ways and there might be an issue with one or the other. Relay B could be bad or the EIS output could be bad.
A quick test for any terminal voltage is to find an appropriate fuse and check for voltage there. For terminal 30, key can be off. For 15R, key in first or second position and for 15, key in second position. For example fuse 10 is terminal 15, fuse 11 is terminal 15R, and fuse 13 is terminal 30.
Your picture is of K40, which is the front fuse box.
Behind it, and partially attached to it is N10/10 Front SAM. They are effectively one module.
As MIKEJ63 says you can check the fuses there for the supplies mentioned.
Terminal 15 ORIGINATES from this SAM (N10/10) and disperses it around the car.
The PREFUSE box (F32 next to the front attery) is a high power fuse box which distributes battery power (From the main battery pre-fuses F52) around the car, and one of the F32 pre-fuses will feed K40 with a constant 12V. K40 has a relay that then provides the "Terminal 15" voltage when the ignition is ON.
Your picture is of K40, which is the front fuse box.
Behind it, and partially attached to it is N10/10 Front SAM. They are effectively one module.
As MIKEJ63 says you can check the fuses there for the supplies mentioned.
Terminal 15 ORIGINATES from this SAM (N10/10) and disperses it around the car.
The PREFUSE box (F32 next to the front attery) is a high power fuse box which distributes battery power (From the main battery pre-fuses F52) around the car, and one of the F32 pre-fuses will feed K40 with a constant 12V. K40 has a relay that then provides the "Terminal 15" voltage when the ignition is ON.
Yes.
Check the module 12V supply against car chassis.
Then check using the module 0V terminal.(there may be more than one 0V terminal and 12V terminal on the module.
They should be the same. If not then you could have a ground fault.
Both measurements should be the same as the module is reporting via diagnostics.
If the R230 matches the documentation I have, then those voltages are in the ballpark for an active CAN network.
Measure voltage on both CAN Lo and CAN Hi against ground with the bus both asleep and awake. With key on, the bus comes awake immediately. With key off, it will take several minutes to half and hour for the bus to sleep. This means if you have the trunk open the bus will stay awake longer but will eventually shut down..
Asleep:
CAN-Lo will have the higher voltage. (~11 volts?)
CAN-Hi will have the lower voltage. (~0.025 volts?)
Awake:
CAN-Lo will be lower voltage (compared to asleep) but still above CAN-Hi. (~4.65 volts?)
CAN-Hi will be higher voltage (compared to asleep) but still below CAN-Lo. (~0.65 volts?)
I put a question mark as the info I have shows for the W220 and others; it is my assumption this also applies to the R230 as it and the S-class were always about two years ahead of the E-class cycle.
If the R230 matches the documentation I have, then those voltages are in the ballpark for an active CAN network.
Measure voltage on both CAN Lo and CAN Hi against ground with the bus both asleep and awake. With key on, the bus comes awake immediately. With key off, it will take several minutes to half and hour for the bus to sleep. This means if you have the trunk open the bus will stay awake longer but will eventually shut down..
Asleep:
CAN-Lo will have the higher voltage. (~11 volts?)
CAN-Hi will have the lower voltage. (~0.025 volts?)
Awake:
CAN-Lo will be lower voltage (compared to asleep) but still above CAN-Hi. (~4.65 volts?)
CAN-Hi will be higher voltage (compared to asleep) but still below CAN-Lo. (~0.65 volts?)
I put a question mark as the info I have shows for the W220 and others; it is my assumption this also applies to the R230 as it and the S-class were always about two years ahead of the E-class cycle.
CAN B asleep it wouldn't give me a reading for some reason? Only on awake it gave me 4.4v on can lo and 0.72 on can hi
Asleep 11 volts on Lo lead and 0.025 volts on Hi lead.
Test each line with multimeter for short or low ohms to chassis. Testing across the lines should show the termination resistor. It's a short to chassis or power that can scramble the communications.
On my W210, a 95-ohm short to chassis on the Hi line was killing the network. Module was a rear window motor tied to CAN network.
Last edited by bbirdwell; Jul 8, 2024 at 09:42 PM.
Have you changed any of the modules on the CAN BUS before this fault started?
I only ask as, frustratingly, the R230 (maybe some others) uses reversed CAN BUS wiring!
I know the CAN BUS plug wiring is reversed between the R171 SLK and R230 SL.
See file attached.
If you connect a module from a different Mercedes model this could cause corruption on the CAN BUS line.
Could cause corruption even if the part number is the same? You are 100% correct about the connector the one I bought is reversed so when i rewired i rewired it the opposite way it looks wrong looking at it but i presume its right? Please correct me if I'm wrong.
I haven't changed any modules before the fault started. Thanks for your help so far i appreciate it
All of the serious warnings in the cluster are on by default and have to be turned off by the module responsible. If CAN B communication is disrupted, the cluster doesn't get these 'I'm OK' messages and starts displaying warnings. What did you do to get past the no start issue?
All of the serious warnings in the cluster are on by default and have to be turned off by the module responsible. If CAN B communication is disrupted, the cluster doesn't get these 'I'm OK' messages and starts displaying warnings. What did you do to get past the no start issue?
I thought i wired the can bus c connector correctly but i had to get a auto electrician in he said its not wired correctly he wired it and got it fired up
I Will look in to the can b tomorrow and hopefully i can solve it
All of the serious warnings in the cluster are on by default and have to be turned off by the module responsible. If CAN B communication is disrupted, the cluster doesn't get these 'I'm OK' messages and starts displaying warnings. What did you do to get past the no start issue?
Auto electrician rewired the CAN c block he got it fired up. The CAN b block is rewired too but i still have the cluster issue he said its not communicating with the drivers side fuse box. I have just changed that with no luck 😒
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