GDII Posted June 3 Report Share Posted June 3 I have just installed a new VR4 LINK into an 89 Galant. I added in a few extra sensors, a MAC valve and an MFD15 gauge. I have wired in a new relay with dedicated power from the battery and this powers a CAN Lambda, 3 port MAC valve and the MFD15 gauge. When powering on the ignition the MFD15 gauge turns on but when shutting off the ignition, the relay turns off but the gauge remains powered on. When I cut the wire to the MAC valve the gauge shut off after doing tests with pulling the CAN JST plug and the fuses that are on the new power feed. I get 12V back feeding through the MAC valve. The OEM location for the boost controller wiring was not suitable so I ran new switched 12V from the relay to the valve then used the OEM wire to the ECU to activate it. So in theory if I wired the MAC valve into the OEM wiring I'd still have the ECU back feeding 12v through the MAC valve and powering up the whole 12V switched system in the engine harness. Now I have not been into the ECU with my laptop yet as I am waiting for the unlock code from the clients supplier. But the question is, is there a setting in the ECU that is putting out high side instead of low side for the boost controller circuit by default. Quote Link to comment Share on other sites More sharing options...
Adamw Posted June 3 Report Share Posted June 3 1 hour ago, GDII said: But the question is, is there a setting in the ECU that is putting out high side instead of low side for the boost controller circuit by default. No, there are no high side drives are fitted in that ecu. Can you do a sketch of how things are wired. Quote Link to comment Share on other sites More sharing options...
GDII Posted June 3 Author Report Share Posted June 3 Hi Adam Ok that is good to know. I used the OEM orange wire and tested it went to the pin on the diagrams I found online as well as checking the pinout of the LINK. I have attached the wiring diagram I have created for the new systems I have put in place. I have highlighted the boost control circuit. Does ECU hold power have anything to do with it? I know this has a stepper motor IACV which I can hear resetting when ignition is turned off. Based on this wiring diagram and my testing the Orange wire (Pin 105) is only connected between the ECU and solenoid. Which is how I have set it up. I'll have to test the solenoid but my understanding is the solenoid is not electrically closed until the ECU grounds the circuit. https://www.galantvr4.org/img.php?id=133167 t=_blank Quote Link to comment Share on other sites More sharing options...
Adamw Posted June 4 Report Share Posted June 4 If the gauge current requirement is very small, there may be just enough current through the pull-up resistor on the boost aux to keep it alive (1.5K to 12V), but if the main MPI relay is off then the pull-up supply should also be off. Since all aux pull-ups are connected to the same rail, Im suspicious perhaps one of the other auxes is back-feeding. The most likely would be the AC relay on aux 4 or the EGR on Aux 2, can you try it with those unplugged? Quote Link to comment Share on other sites More sharing options...
GDII Posted June 4 Author Report Share Posted June 4 I have tried disconnecting those 2 outputs and it still has 12V on the boost control wire. The 12V feed to the boost controller is still disconnected too. I have loaded the MAP into the ECU but it doesn't seem to have changed anything. Even deactivating the Aux doesn't change it. I get 11.2v back feeding but 12.3v on the 12V feed side. So there is a little bit of a voltage drop on the back feed loop. I plugged in the standard ECU and it doesn't get 12v on the solenoid side. I guess there is something different with the architecture of the LINK vs OEM. And a second test I get 12v from the AC on Aux 4. So that means something is feeding it 12V from elsewhere? Quote Link to comment Share on other sites More sharing options...
Adamw Posted June 4 Report Share Posted June 4 13 hours ago, GDII said: When powering on the ignition the MFD15 gauge turns on but when shutting off the ignition, the relay turns off but the gauge remains powered on. How did you confirm the relay is turning off? From what you have described so far I dont think it is. When the gauge remains on with the ignition off, what happens if you unplug that relay, does everything then shut down? I suspect that relay is being held closed due to a backfeed through the boost solenoid and out of pin 102. That relay coil should be connected to pin 110 so there is no chance of a loop if the MPI relay opens quicker than the new relay. Quote Link to comment Share on other sites More sharing options...
GDII Posted June 4 Author Report Share Posted June 4 The relay makes an audible click that you can also feel when touching the relay. However you do make a valid point about this relay being wired to 110 instead of 102 or 107. This car seems to have a factory turbo timer or something holding the power on when the the key is removed. The relay shuts off after the ECU hold power system shuts off but it did seem to stay active when this all happened. The fuse on the relay being removed shut off the gauge. I haven't actually tested the gauge remaining on since I found the 12V feed from the ECU. But I can rejoin it. I'll rewire the relay ignition to 110 tomorrow and see what that gives me. It might explain the 12V feed out of the ECU but if it doesn't then where is the next best place to look? The OEM ECU doesn't power the boost controller wire even with the relay active wired to 102/107. I will get back to you on this. Thanks for your help so far. Quote Link to comment Share on other sites More sharing options...
GDII Posted June 4 Author Report Share Posted June 4 Update: Rewired the new relay to the Ignition switch pin 110 rather than the MPI hold power relay. The MDF15 gauge shuts off now even with the boot control solenoid connected. So if I had done this in the first place I would not have noticed the 12v feed from the ECU. Is this still a problem or am I overthinking it? Quote Link to comment Share on other sites More sharing options...
GDII Posted June 5 Author Report Share Posted June 5 I have tested the boost solenoid and it works out so even though it seems to be back feeding 12V it appears to be working as normal. Quote Link to comment Share on other sites More sharing options...
Adamw Posted June 5 Report Share Posted June 5 Its not a back feed, there is a 12V pull-up resistor on all auxes, so when the ecu is powered but the aux is off, there will be 12V present on the aux. It is only a few mA, not enough to power anything, but it is needed for devices that need a square wave PWM or frequency signal such as tacho's, solidstate relays etc Quote Link to comment Share on other sites More sharing options...
GDII Posted June 5 Author Report Share Posted June 5 10 hours ago, Adamw said: Its not a back feed, there is a 12V pull-up resistor on all auxes, so when the ecu is powered but the aux is off, there will be 12V present on the aux. It is only a few mA, not enough to power anything, but it is needed for devices that need a square wave PWM or frequency signal such as tacho's, solidstate relays etc Thanks for confirming. Good to know this is normal. I'll tidy everything up and pass the car onto the tuner to let them sort the rest. Quote Link to comment Share on other sites More sharing options...
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