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Discussion Starter · #1 ·
Hopefuly someone can help me with this.

I have a 1999 Viggen convertible that's been standing about a month. All of a sudden it now buzzes under the dash when ignition turned on, turns over but will not fire up and start. Buzzing could be due to what I found out next.

The red cable to the air con compressor had been shorting out. I have cured this but still have a car that will not start.

Fuses 38, 26 & 16b all measure between 8.4 & 9 volts
Taking these fuses out shows the voltage still on the lower side of the fuse holder pins and not the top. (Is this the feed out of the fuseholder?)

The only common item in these circuits is the T7 ECU which when removed clears the 9 volts on the fuses as mentioned above.

Removing the connector from the Lambda sensor under the hood clears this 9v from showing up on the lower pin of number 38 fuseholder but its still present in the other two fuses.

Does this prove that its the ECU at fault and not something connected to the ECU? With the ECU disconnected I measured the voltage of all the pins on the wiring loom ECU connector. None of these show the 9v I see when the ignition is on the on position and the ECU is connected.

I have tried systematically removing relays and T7 Connectors around the car, turning the ignition to the on position, I always still get around 9v on the three above fuses with the ECU attached.

If the T7 B235R ECU is blown what other T7 ECU can I used that will work enough to drive to somewhere with a tech2 and I guess the flash files for a 1999 Viggen convertible.
 

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Where are you located? Someone on here with a Tech 2 might be near enough to give you a hand.
 

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Are you sure the battery is fully charged?

I didn't realize they made Viggen 'verts in '99. Over here we only got Lightening Blue 3-door hard tops in '99. The rest were T-5's. What color is yours?
 

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Discussion Starter · #7 ·
Some developments...

Measuring the voltage to pin one of the t7 ECU connector with the ECU in or out and ignition switched on shows no voltage.

The circuit diagram seems to suggest this should power the DIC as well. The relays that need to turn on are switched to ground through the ECU. This makes no sense to me as I thought pin 1 needed voltage to turn the ECU on.

Tried a DIC and different ECU from a known working t7 car and no change.

It's as if the DIC and ECU need voltage on pins 10 and 1 but the circuit doesn't show how this is achieved. Reluctant to take all the dash out and find out myself :)
 
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