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Red/blue is the 12v power to just about every sensor on the engine, it has two big splices where 6-8 wires are all spliced together, the main power comes from the MFI/DI relay..
Since you have the 12v at the MAF but only 5.8v at the ISC, your issue will closer to the splice near the the ISC...
MAF, ISC, both cam sensors, all change over valves, purge valve, ect all are powered by the red/blue and go through one of the two big splices...
If it is a bad connection and not a "shorted wire" you could do a temporary jumper wire anywhere near the ISC, and see if she runs.....
Then get down to the nitty gritty and trace the haness to pinpoint and repair the issue...
Awesome thanks, I hope this is it, definitely seems to make sense... "two big splices where 6-8 wires are all spliced together" anyone know where this spot is to keep me from digging?
Okay this gets a little convoluted at least for me.
term 86 at MFI relay gets power from fuse C1 through weld point 25. Main relay at DME pin27
grounds coil and term 87 feeds power to weld point 26. Pin 8 at X connector 59/1 receives that 12volts and feeds to weld point 9 which powers the idle speed control.
DME pin 54 gets power from weld point 26 which in turn it uses to power the variocam solenoids.
Okay this gets a little convoluted at least for me.
term 86 at MFI relay gets power from fuse C1 through weld point 25. Main relay at DME pin27
grounds coil and term 87 feeds power to weld point 26. Pin 8 at X connector 59/1 receives that 12volts and feeds to weld point 9 which powers the idle speed control.
DME pin 54 gets power from weld point 26 which in turn it uses to power the variocam solenoids.
hope this is of some use….
The DME doesn't power the variocam solenoids, it "grounds" the solenoids to activate them....
BTW ; that brings up an old memory of a variocam solenoid that was causing a low voltage on the red/blue circuit due to a partially shorted solenoid ... Disconnect both variocam solenoids to see if the 12v power returns to normal..
Last edited by Porschetech3; 09-01-2023 at 02:29 PM.
The DME doesn't power the variocam solenoids, it "grounds" the solenoids to activate them....
BTW ; that brings up an old memory of a variocam solenoid that was causing a low voltage on the red/blue circuit due to a partially shorted solenoid ... Disconnect both variocam solenoids to see if the 12v power returns to normal..
This exchange was posted on Rennlist site and sounds interesting and accurate.
looks like the vario cams get 12volts from weld point 9 as well as the idle speed positioner.
You could take a gander at the X59/1 connector where pin 4 and pin 8 reside. Might still have iffy connection in connector.
looks like pin 4 supplies power to injectors and coils if I’m not mistaken, which is entirely possible and I’m always open to criticism and or correction.
Originally Posted by jumpy chunky;[url=tel:18992954
18992954[/url]]Porschestien,
looks like the vario cams get 12volts from weld point 9 as well as the idle speed positioner.
You could take a gander at the X59/1 connector where pin 4 and pin 8 reside. Might still have iffy connection in connector.
looks like pin 4 supplies power to injectors and coils if I’m not mistaken, which is entirely possible and I’m always open to criticism and or correction.
Thanks, I will definitely be looking at the x59’s and RE/BL circuit in the engine harness next.
Yea that post only tells half the story with no conclusion...
It also insinuates that the vario-cam solenoids gets power from the DME, but it does not....Vario-cam solenoids gets power straight from the battery through the MFI/DI relay and two splices and the x59/1 connector
Originally Posted by jumpy chunky
This exchange was posted on Rennlist site and sounds interesting and accurate.
This is correct VVVVV ...
Originally Posted by jumpy chunky
Porschestien,
looks like the vario cams get 12volts from weld point 9 as well as the idle speed positioner.
You could take a gander at the X59/1 connector where pin 4 and pin 8 reside. Might still have iffy connection in connector.
looks like pin 4 supplies power to injectors and coils if I’m not mistaken, which is entirely possible and I’m always open to criticism and or correction.
The DME does not control the engine by controlling the power, it controls the "ground circuit" to the already powered components, ie. injectors , coils, solenoids, switches ect.. The only power the DME sends is a "5v reference voltage" to get feedback from hall sensors, rheostats, and variable resisters type sensors...
All DME's, ECU's, EEC's, I have ever had the pleasure to troubleshoot work in this way, they are a big fast grounding device...
Last edited by Porschetech3; 09-02-2023 at 02:51 PM.
Thanks, I will definitely be looking at the x59’s and RE/BL circuit in the engine harness next.
Disconnect the purge valve, the change-over valve for the resonance flap, the change-over valve for SAI , also the change-over valve for Tiptronic if equipped,leave the vario-cam solenoids unplugged, then check to see if the 12v to red/blue at the ISC is returned to normal...
If not then jump to mid-point at the x59/1 pin 8 to see if 12v is there...This should eliminate half the wiring as a possible ..
Low voltage on the red/blue circuit will keep the injector relay from even turning on.....
I'm not really sure what's what as far as these, but here is what I looked at today...
Valve or Pump in the fuel expansion / evap tank in the passenger fender well:
09-01-2023, 01:22 PM
