'V ref' reading ~12V... Yikes.
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'V ref' reading ~12V... Yikes.
So, I recently removed the EM harness from my turbo swapped S4 GXL. I depinned all of the wires and connectors that I didn't need. (2O, 2P, 2M, 2N, 2K, and 3D)
Yesterday I reconnect everything and try to start the car. I noticed that the fuel pump didn't prime. The car sputtered and tried to start about five times. Pressing the throttle a bit didn't help because it felt as though there was no throttle pedal.
Today I remove the three ECU plugs and check voltage to a few wires with key to "ON"... The main thing that really stood out was the 'V ref' voltage reading full voltage as opposed to the 4.5~5.5V that it should be seeing. Just to be sure, I check the boost sensor V ref, the AFM V ref, and the TPS V ref. They all read full voltage. (Roughly 12V.)
The car ran great about two weeks ago, before I had "cleaned-up" the wiring harness. This is the same issue that ruined my old Power FC. I now have stock components. (N333 ECU) - I don't understand where the 'V ref' wire gets it's signal.
Yesterday I reconnect everything and try to start the car. I noticed that the fuel pump didn't prime. The car sputtered and tried to start about five times. Pressing the throttle a bit didn't help because it felt as though there was no throttle pedal.
Today I remove the three ECU plugs and check voltage to a few wires with key to "ON"... The main thing that really stood out was the 'V ref' voltage reading full voltage as opposed to the 4.5~5.5V that it should be seeing. Just to be sure, I check the boost sensor V ref, the AFM V ref, and the TPS V ref. They all read full voltage. (Roughly 12V.)
The car ran great about two weeks ago, before I had "cleaned-up" the wiring harness. This is the same issue that ruined my old Power FC. I now have stock components. (N333 ECU) - I don't understand where the 'V ref' wire gets it's signal.
#2
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it comes directly from the ECU. you have some cross continuity still going on for it to be seeing 12v so the wiring harness is faulty somewhere.
remove or temporarly cut the 5v ref from the ECU and check to see if it is still putting out only 5v directly from the ECU or the stock ECU may be fried as well. from there continue disconnecting anything that has a Vref connection to see if something may be shorting out internally that also has a 12v input like OMP(if it was an S5), AFM, pressure sensor, etc. if with them all disconnected it still showing 12v then it's obviously the Vref wire in the main harness is touching a 12V hot wire somewhere and will need to be cut open and dissected or replaced.
remove or temporarly cut the 5v ref from the ECU and check to see if it is still putting out only 5v directly from the ECU or the stock ECU may be fried as well. from there continue disconnecting anything that has a Vref connection to see if something may be shorting out internally that also has a 12v input like OMP(if it was an S5), AFM, pressure sensor, etc. if with them all disconnected it still showing 12v then it's obviously the Vref wire in the main harness is touching a 12V hot wire somewhere and will need to be cut open and dissected or replaced.
Last edited by RotaryEvolution; 06-03-12 at 12:31 PM.
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Luckily the ECU is okay. I've found that when the atmospheric pressure sensor (near passenger side kick panel) is plugged in, the voltage is well above the necessary 4.5~5.5V. With key to "ON" and pressure sensor unplugged, I get ~4.9V at the 'V ref' wire on the atmospheric pressure sensor plug. My problem lies somewhere in that bit of wiring... Maybe even the sensor itself.
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Where would it be rubbing at? At the sensor plug or something??
I just checked the 'V ref' pin at the ECU plug with key to "ON" and now it is showing ~12V. It wasn't doing that before... So, I unplugged the boost sensor and it went away. This is starting to become a clusterfuck.
I just checked the 'V ref' pin at the ECU plug with key to "ON" and now it is showing ~12V. It wasn't doing that before... So, I unplugged the boost sensor and it went away. This is starting to become a clusterfuck.
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I'll keep looking around.
What would cause the fuel pump not to prime? I jumpered the check connector yesterday, and it runs. It just won't prime when I turn the key to the "ON" position.
What would cause the fuel pump not to prime? I jumpered the check connector yesterday, and it runs. It just won't prime when I turn the key to the "ON" position.
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#8
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You might want to check pin 2R which is a ground thus w/key to on it should have 0 volts. This ground is associated w/the ground of the AFM and its related fuel check connector, which if poor would prevent the fuel pump from turning on after the check connector is jumpereed and key to on.
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doesn't prime, it either runs with the key in "start" or when the ECU sees RPM and the AFM is not fully closed
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^ That's interesting. My car has always primed for a few seconds with key to "ON". It primed two weeks ago when I drove it. Perhaps I don't have an issue when it comes to that. I still have the V ref issue. :-/
I checked 2R with key to "ON" at the ECU plug and at the AFM and got 0V. So, that checks out to be just fine.
I have yet to look in the FSM at the two orange plugs near the atmospheric pressure sensor. I only get this problem when the connector with 13 wires is plugged in. Those plugs connect to the dash harness?
I checked 2R with key to "ON" at the ECU plug and at the AFM and got 0V. So, that checks out to be just fine.
I have yet to look in the FSM at the two orange plugs near the atmospheric pressure sensor. I only get this problem when the connector with 13 wires is plugged in. Those plugs connect to the dash harness?
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^ That's interesting. My car has always primed for a few seconds with key to "ON". It primed two weeks ago when I drove it. Perhaps I don't have an issue when it comes to that. I still have the V ref issue. :-/
I checked 2R with key to "ON" at the ECU plug and at the AFM and got 0V. So, that checks out to be just fine.
I have yet to look in the FSM at the two orange plugs near the atmospheric pressure sensor. I only get this problem when the connector with 13 wires is plugged in. Those plugs connect to the dash harness?
I checked 2R with key to "ON" at the ECU plug and at the AFM and got 0V. So, that checks out to be just fine.
I have yet to look in the FSM at the two orange plugs near the atmospheric pressure sensor. I only get this problem when the connector with 13 wires is plugged in. Those plugs connect to the dash harness?
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My apologies. It definitely has 7 pin positions on the longest row, meaning it is FEM-02. I know for sure that it has two black/white wires with 12V with key to "ON". That is the plug that is giving me issues. I've checked the EM harness and haven't found any open wires. I've also inspected each plug with a V ref wire... Nothing touching any other voltage sources.
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My apologies. It definitely has 7 pin positions on the longest row, meaning it is FEM-02. I know for sure that it has two black/white wires with 12V with key to "ON". That is the plug that is giving me issues. I've checked the EM harness and haven't found any open wires. I've also inspected each plug with a V ref wire... Nothing touching any other voltage sources.
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It does result in zero. I don't know what the ECU is doing without that plugged in. Perhaps I am just making things more complicated in my mind. I figured maybe that the front harness was feeding voltage through the FEM-02 connector to the wrong wire in the EM harness. I cannot find the FEM connectors in the FSM.
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It does result in zero. I don't know what the ECU is doing without that plugged in. Perhaps I am just making things more complicated in my mind. I figured maybe that the front harness was feeding voltage through the FEM-02 connector to the wrong wire in the EM harness. I cannot find the FEM connectors in the FSM.
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~5V from the V ref pin on the ECU and ~12V from the depinned ECU V ref wire.
Are there any other items that use the V ref signal other than the AFM, TPS, boost sensor, and atmospheric pressure sensor?
Are there any other items that use the V ref signal other than the AFM, TPS, boost sensor, and atmospheric pressure sensor?
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In case the resistor is not the problem.
Both the Boost and ATP sensor have a B/W wire that has voltage of 12 volts w/key to on. So perhaps you might depin one of these B/W wires and recheck the voltage on the depinned Vref wire and see if the voltage drops from 12 volts or not. If not, then depin the B/W wire at the other sensor and once again check the voltage on the depinned Vref wire. If it drops then repin the 1st B/W wire that was depinned and w/all of these sensors connected except for the one recently depinned make sure the voltage is still not 12 volts. If so then you probably narrowed down your problem.
Both the Boost and ATP sensor have a B/W wire that has voltage of 12 volts w/key to on. So perhaps you might depin one of these B/W wires and recheck the voltage on the depinned Vref wire and see if the voltage drops from 12 volts or not. If not, then depin the B/W wire at the other sensor and once again check the voltage on the depinned Vref wire. If it drops then repin the 1st B/W wire that was depinned and w/all of these sensors connected except for the one recently depinned make sure the voltage is still not 12 volts. If so then you probably narrowed down your problem.
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I depinned the B/W on the boost sensor first and read ~12V on the depinned V ref wire.
I depinned the B/W wire on the ATP sensor while the boost sensor B/W wire was still depinned... 0V on the depinned V ref wire.
I repinned the boost sensor B/W wire. ~12V on the depinned V ref wire.
This would mean that it is this particular B/W between the ATP and Boost sensor that is giving me issues then. Correct?? Wait... I've not yet tried the variable resistor.
I depinned the B/W wire on the ATP sensor while the boost sensor B/W wire was still depinned... 0V on the depinned V ref wire.
I repinned the boost sensor B/W wire. ~12V on the depinned V ref wire.
This would mean that it is this particular B/W between the ATP and Boost sensor that is giving me issues then. Correct?? Wait... I've not yet tried the variable resistor.