Author Topic: Voltage Difference  (Read 171 times)

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Voltage Difference
« on: August 15, 2018, 01:46:15 PM »
I have 2008 159 2.2 JTS Selespeed

When I measure voltage on battery terminal and via MES it measures 0.5v lower (cold in the morning)

EDIT: The voltage is actually matching on ECU but 0.5v lower when connected to Selespeed computer

Is this a concerning difference ? or natural ? because I've been having a bunch of electrical problems that I'm trying to resolve. I'm was having below issues

  • Selespeed goes to neutral while driving
  • Selespeed misses even gears and jumps to next
  • Selespeed gets stuck in neutral and can't put gears in other than R (sometime for 1 minute, 5 minutes, 1 hour or 4 hours !!)
  • Selespeed goes into limp mode so I can select only (R-1-2-3 or R-1-2 sometimes)
  • VDC / ASR warnings
  • Speedo & Tacho die (but reading is still available on MES) and it happens in conjunction with the limp mode)
  • VPS error and car doorlock clicks randomly itself even while driving and when above errors come up it occasionally happens at the same time.) Yesterday I closed door while engine is on and closed door. Later it locked the car by itself!! Luckily I was in my carpark so I had to get spare key and manually unlock with key.
  • in MES mainly getting CAN line & Minikrypt (no idea what this is) errors at the moment
  • Sometime the car starts straight away and sometime it takes 2-3 attempts but it's not really starter struggles to start. it feels more like the car forgot to inject fuel at the same time :(

It spent 2 weeks in AR specialist garage for repair & service with no difference afterward so I decided to take it on my hands. The mechanic was blaming ABS module for all these problem but I don't think a single module error can cause such wide range of issues.

I already strengthened all earths under the hood, fitted a brand new battery (85a/800cca), checked alternator, visually checked main CAN lines under the footwell and cleaned all fuseboxes and finally it made few progress.

  • Selespeed neutral & stuck issue seems to be gone. (probably fixing gearbox to chassis earth fixed this problem)
  • VDC errors and limp mode don't always happen together (when limp mode happens VDC error comes along but now sometime it's only VDC errors without limp mode, now the chances are more likely from 10:0 to 6:4)
  • Gear changes much smoother than before

Other than all those problems the car runs good.

So back to the "Voltage" topic I'm suspecting ECU (maybe) or Body Computer's weakened connection (external/or internal) may cause this lower reading and causes random faults rather than individual sensors or modules doing so. I guess Body Computer is more responsible for those type of problems so just want to find out if the voltage difference between Engine computer and Selespeed computer is really concerning issue or not.
« Last Edit: August 16, 2018, 10:38:44 AM by ragazzo »