Sti V6 Problem ECU broke?
14 February 2010, 04:07 PM
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Sti V6 Problem ECU broke?
I was wondering if maybe someone could help me out, a friend has a Version 6 STi and thinks his Mine's ECU may have crapped out yesterday. He has a high idle problem which was originally diagnosed it as a bad IACV. It's the sensor off the throttle body with the 6 pin square connector on it.He has tried a spare IACV that he has, and it's doing the same thing (idling at 2000 RPM). No vacuum leaks and brand new MAF sensor.
Has anyone got access to a volt meter? or know the correct readings? If so, here's what he is seeing. The two center pins have 12V with the connector off, key in the on position. Best I can tell, that's correct. The bottom two wires (I forget the color) one of them ramps to 1.4 volts with the key initially turned on or off (first 6 seconds or so). I'm pretty sure that's right. The blue/black wires are on the top. Those, I'm pretty sure, go to the other coil inside the IACV. They never get a voltage from the ECU, key on or off. I believe that the ECU is faulty, that's why I never see a voltage on blue or black. It should only get a voltage when the key is turned on or off for the first 6 seconds or so could anyone tell me if you see any voltage on blue or black wires?
Thanks in advance!!!
Has anyone got access to a volt meter? or know the correct readings? If so, here's what he is seeing. The two center pins have 12V with the connector off, key in the on position. Best I can tell, that's correct. The bottom two wires (I forget the color) one of them ramps to 1.4 volts with the key initially turned on or off (first 6 seconds or so). I'm pretty sure that's right. The blue/black wires are on the top. Those, I'm pretty sure, go to the other coil inside the IACV. They never get a voltage from the ECU, key on or off. I believe that the ECU is faulty, that's why I never see a voltage on blue or black. It should only get a voltage when the key is turned on or off for the first 6 seconds or so could anyone tell me if you see any voltage on blue or black wires?
Thanks in advance!!!
14 February 2010, 04:29 PM
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Well, I was just getting ready to start a new thread but Lee beat me to it 
. Thanks, mate! Here's the full rundown of what I did:
Hey Guys -
I've got a weird problem with my JDM Version 6 STi. On cold start, the tach starts at 1500 RPM and climbs up to 2500. It revs cleanly and drives. I initially thought it was the IACV. I took it out, cleaned it, same problem. Got the car home from the workshop and I replaced the IACV with a spare I had from a previous motor. Same issue.The O-rings was also good.
So we ordered a MAF since the A/F's were all over the place and it seemed to be a good place to start since mine has 95,000 KM on it. Brand new MAF element from Subaru, same issue although the A/F's are now reasonable. Then I proceeded to check the throttle butterfly, it's closed, no sticking. I also did a boost leak check by capping the hose (pre-maf) and feeding 10 psi of air via my air diverter valve vacuum hose. She holds 10 psi and bleeds down slow. The slow bleed could be coming from anywhere and I would consider it normal. If you pull a small vacuum hose off the inlet the 10 psi pressure dissipates in a matter of seconds. Not a popped hose or coupler.
So I'm back looking at the IACV circuit. First we left the connector on the IACV, disconnected the ECU and checked the ohm-age with a multimeter. I'm seeing about 50 ohms on A134 (pins 5-->14 and 6-->15). This resistance is consistent with readings from the other IACV. We also ohm'd the wires from the ECU connector pins 5,6, 14, 15 to the IACV connector. Looks good, no grounds, shorts across or open wires. Next test was voltage. And this is where it gets weird....
The way I see it, the IACV is made of two internal coil packs. Looking at the connector, the two bottom wires (forgot the colors) make up one coil, the two center wires feed 12V to each coil, and the top two (blue and black) make up the second coil. One coil serves to drive the IAC piston in, the other coil draws it out. At least that's how I see it operating. With the key on I get 12V at the two center wires (correct). On one of the bottom wires I see the voltage ramp up to 1.4V when the key is initially turned. No doubt serving to energize the coil to initially move the IACV. On the black and blue wires though, I see no voltage. Nothing with the key initially turned on or off either. I'm wondering if maybe the idle circuit in my ECU is knackered. Unfortunately I don't have a spare ECU here at the moment to test with. That's why I'm asking for help
Would anyone be so kind as to disconnect their IACV connector (6 pin on top of the throttle body) and check the blue or black wires for voltage when the key is initially turned on or off? It would have to be a 99' or 00' model as the earlier Impreza used a three wire IACV. I would be deeply indebted as I'd rather not drop the money on a spare ECU if the problem lies elsewhere. Anyone who has seen a similar issue, feel free to chime in!
Cheers,
Ryan
. Thanks, mate! Here's the full rundown of what I did:Hey Guys -
I've got a weird problem with my JDM Version 6 STi. On cold start, the tach starts at 1500 RPM and climbs up to 2500. It revs cleanly and drives. I initially thought it was the IACV. I took it out, cleaned it, same problem. Got the car home from the workshop and I replaced the IACV with a spare I had from a previous motor. Same issue.The O-rings was also good.
So we ordered a MAF since the A/F's were all over the place and it seemed to be a good place to start since mine has 95,000 KM on it. Brand new MAF element from Subaru, same issue although the A/F's are now reasonable. Then I proceeded to check the throttle butterfly, it's closed, no sticking. I also did a boost leak check by capping the hose (pre-maf) and feeding 10 psi of air via my air diverter valve vacuum hose. She holds 10 psi and bleeds down slow. The slow bleed could be coming from anywhere and I would consider it normal. If you pull a small vacuum hose off the inlet the 10 psi pressure dissipates in a matter of seconds. Not a popped hose or coupler.
So I'm back looking at the IACV circuit. First we left the connector on the IACV, disconnected the ECU and checked the ohm-age with a multimeter. I'm seeing about 50 ohms on A134 (pins 5-->14 and 6-->15). This resistance is consistent with readings from the other IACV. We also ohm'd the wires from the ECU connector pins 5,6, 14, 15 to the IACV connector. Looks good, no grounds, shorts across or open wires. Next test was voltage. And this is where it gets weird....
The way I see it, the IACV is made of two internal coil packs. Looking at the connector, the two bottom wires (forgot the colors) make up one coil, the two center wires feed 12V to each coil, and the top two (blue and black) make up the second coil. One coil serves to drive the IAC piston in, the other coil draws it out. At least that's how I see it operating. With the key on I get 12V at the two center wires (correct). On one of the bottom wires I see the voltage ramp up to 1.4V when the key is initially turned. No doubt serving to energize the coil to initially move the IACV. On the black and blue wires though, I see no voltage. Nothing with the key initially turned on or off either. I'm wondering if maybe the idle circuit in my ECU is knackered. Unfortunately I don't have a spare ECU here at the moment to test with. That's why I'm asking for help
Would anyone be so kind as to disconnect their IACV connector (6 pin on top of the throttle body) and check the blue or black wires for voltage when the key is initially turned on or off? It would have to be a 99' or 00' model as the earlier Impreza used a three wire IACV. I would be deeply indebted as I'd rather not drop the money on a spare ECU if the problem lies elsewhere. Anyone who has seen a similar issue, feel free to chime in!
Cheers,
Ryan
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