Help! buzz in pwr/train relay

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cdover2005

Member
First attempt starting the Goblin today and unfortunately it won't start. Here is what I was able to diagnose so far.

- The Pwr/Train Relay is buzzing when the ignition is in the On position. Check Engine light pulses in sync with the buzz.
- Checked grounds and I have continuity at all grounds and they are all connected. (11.5 VDC at lugs). I went through the harness and relocated 2 that I thought were the problem.
- Fuel pump does not prime.
- Throttle Blade does not move with the gas pedal.
- No cranking when ignition is in Start position.
- No communication with my OBDII reader when plugged in.

I searched the thread for similar issues and most seem ground related but this one has me baffled.
 

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Gtstorey

Goblin Guru
11.5v is too low and you need to charge the battery. That likely isn't your only problem though. Sounds like you also have a data wire problem.
 
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Gtstorey

Goblin Guru
So it's hard to follow what you are checking voltages on from the video, but if you are getting less that battery voltage at anything other than a sensor input/output then you have a bad (loose/dirty) connection somewhere. I guess there is a chance that the BCM may be damaged and it has the bad connection but doubtful.

The buzzing sound on the relay is it not getting enough power to stay energized.
 
C

cdover2005

Member
Gtstorey said:
So it's hard to follow what you are checking voltages on from the video, but if you are getting less that battery voltage at anything other than a sensor input/output then you have a bad (loose/dirty) connection somewhere. I guess there is a chance that the BCM may be damaged and it has the bad connection but doubtful.

The buzzing sound on the relay is it not getting enough power to stay energized.
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I will charge the battery up and clean the connections to see if I get a different result. thanks for the response
 
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Gtstorey

Goblin Guru
If I had this problem I would start back tracing the wiring until I see where I'm losing the battery voltage. I typically will start by checking the positive voltage to a known good ground by running a wire from the negative terminal of the battery.

What voltage are you getting at the B+ post on the fuse box. That should be supplying the battery voltage to one leg of the relay. I don't have the wiring diagram with me to check to see if the relay is closed by positive voltage from the BCM or by grounding.
 
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cdover2005

Member
B+ post is getting 12v. Oddly when the key is off voltage is 12v across pin 30 and 87, and 0v at 85 and 86. Which is normal I think. But when the key is on, the volt drops to about 5 v across both. This is with no relay installed. I wonder if it is related to the problem I had when thinning the harness that you helped me with. It was something with the clutch position sensor
 
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Gtstorey

Goblin Guru
On my later model wire diagram you should be getting 12v across 87 to 30. Are you saying relay is out and you put your red probe on 87 and black on 30 you read positive 12v? If so you likely have something shorting to ground but maybe only partial since you haven’t started a fire or burnt up wires. That relay feeds a lot of stuff on the later cars and especially the turbo. Most of the engine sensors, coils, injectors and more.

what donor to you have?
 
C

cdover2005

Member
Gtstorey said:
On my later model wire diagram you should be getting 12v across 87 to 30. Are you saying relay is out and you put your red probe on 87 and black on 30 you read positive 12v? If so you likely have something shorting to ground but maybe only partial since you haven’t started a fire or burnt up wires. That relay feeds a lot of stuff on the later cars and especially the turbo. Most of the engine sensors, coils, injectors and more.

what donor to you have?
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09 ss/tc
 
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Gtstorey

Goblin Guru
One at a time pull the following fuse and see if you lose battery voltage across pins 87 and 39
EXH
PCM/ECM
INJ
ENG VLV SOL
AC CLUTCH
 
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Gtstorey

Goblin Guru
I'll study the wiring diagrams for the ecm/pcm fuse when I get a chance. Are you getting 5V on one side of the ECM/PCM fuse? When you aren't getting voltage what is your resistance to ground? When you pull the ecm/pcm fuse do you no longer get battery voltage across pins 87 to 30?
 
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cdover2005

Member
cdover2005 said:
yes those are voltages to ground. when the ignition is in on and I pull the ecm/pcm fuse the 5 volts on pin 30 goes away. I am really starting to suspect the ecm is the problem
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I partially removed the harness from the car and removed tape around the X5 plug. I found a ground at C2 that was not attached to anything. I grounded it and am putting everything back together now. Fingers crossed I'll let you know what happens.
 
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Gtstorey

Goblin Guru
A missing ground likely won't cause voltage to show at the output side of the relay. I just reread my post 10 from last night and realized that I missed typed. You should NOT get 12v across pin 87 to 30.
 
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