808 component id and use

Holden/Delco Tuning. ALDL, OBD 1.5. Circa 1989 to 2004.
Dazza92VP
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808 component id and use

Post by Dazza92VP »

Need a bit of help with I’d of a component on an 808 I think it’s a resistor but not sure and what pins in the loom it’s possibly attached to as it decided to let out the smoke it’s fitted into a vs s3 running a modified 424 loom changes to suit an 808 I repinned it but obviously got something wrong but Im not sure which pin in the loom is the issue as this was a working ecu until then and I’m hoping I can bring the dead ecu back to life with just a new resistor or what ever that component is
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Re: 808 component id and use

Post by bf6379 »

It looks to me like it is the 0.103 ohm resistor in the (unused) INJSENSE circuit. You may have accidentally connected power to the D9 pin.
What I am confused about is that it looks like one end of it is connected to pin 50 of U12, which is VCC (unless I am counting the pins wrong). The circuit diagram doesn't show this resistor connected to VCC. Does IC U12 (in your pic with 79435 stamped on it) have one chamfered corner, or an indentation near a corner? If I was at home I would have an 808 to look at and I could give a better answer...
Dazza92VP
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Re: 808 component id and use

Post by Dazza92VP »

Ok so I may have swapped the injectsense wire from the 424 harness into there. i assumed that it was on the pinouts for 12p and figured that it couldn’t hurt to have it hooked up and reading if it’s there anyway and yes it does go into u12 so I may have deep fried this thing more than intended because it doesn’t even pulse the injectors and engine light doesn’t seem to want to put out flash codes but does turn on and off, fuel pump turns on and off and thermo fan doesn’t come on
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Re: 808 component id and use

Post by bf6379 »

I was thinking that may have been what you did.
On the 424, there is a connection from the +12V side of the injectors to pin D7. Is that what you connected to D9?
Ignore what I said about the resistor being connected to pin 50. I started counting at the wrong pin. It is connected to pin 5, which agrees with the circuit diagram.
The INJSENSE signal doesn't need to be used on the 808. Unless more damage has been done, then your 808 may only be objecting to the fact that the resistor has gone open-circuit and allowing pin 5 to go high. Can you see any other damage to the circuit board, including burnt tracks?
0.103 ohms is almost a short-circuit anyway. The INJSENSE input isn't used, so in normal operation there would be no voltage across the resistor. You could try connecting pin D9 to ground and see if that gives you back some functionality.
Dazza92VP
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Re: 808 component id and use

Post by Dazza92VP »

Yea that’s what I connect to it I’ve never used it before on any of the other swaps I’ve done but this time I thought it there why not didn’t think it would be an issue but oh well sometimes have to learn the hard way. I’ll try grounding it see if anything come back to life but I suspect it won’t had a good look at the board and that’s the only damage externally I can see
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Re: 808 component id and use

Post by pman92 »

Ive got a couple of questions

What's the intended purpose of the INJSENSE circuit? Even though its not used.

Are there complete circuit diagrams of the 808 getting around?
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bf6379
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Re: 808 component id and use

Post by bf6379 »

pman92 wrote:Ive got a couple of questions

What's the intended purpose of the INJSENSE circuit? Even though its not used.

Are there complete circuit diagrams of the 808 getting around?
The INJSENSE pin (D9) goes to ground via the 0.103 ohm 2W resistor, with both sides of the resistor connected to pins on U12 labelled ISENSE+ and ISENSE-. U12 also has an injector low-side voltage sensing input labelled VSENSE. All of this suggests that the INJSENSE is a current sensing circuit, with the 0.103 ohm resistor being a current shunt. The intention may have been to provide a ground return for the injectors via this resistor by connecting pins D3/D10 to pin D9 instead of connecting them directly to ground.
However, there are a few anomalies:

Eight x 12 ohm injectors in parallel would put about 8 amps through this resistor. So anything above 30% duty cycle would exceed the 2 Watt rating.
The injector ground pins are D10 and D3, and injector control are D15 and D16. Both signals use 2 pins each, presumably to increase current capacity, but INJSENSE only has one pin.



Maybe Delco designed it to be used with higher resistance injectors, or on 4 cylinder applications. The INJSENSE input wasn't used on VN or VP V6s either.

The circuit diagrams that I have are for the 1227165, which other than having an additional IC (U2) for the 8192 baud ALDL steam, is identical to the 1227808.

I'm surprised that the circuit diagrams are not already on this site. I will try to post them.
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Re: 808 component id and use

Post by pman92 »

Could the injsense have been intended for throttle body injection where there is a single injector?

If you could post them that would be awesome. I'm really keen to have a look

Edit: just found your other post. Cheers!
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Re: 808 component id and use

Post by bf6379 »

pman92 wrote:Could the injsense have been intended for throttle body injection where there is a single injector?

If you could post them that would be awesome. I'm really keen to have a look

Edit: just found your other post. Cheers!
No worries.

Single injector... That's possible.
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Re: 808 component id and use

Post by antus »

D8 and D9 are linked in a loop for single TBI (low impedance) injector. This is the only diagram Ive ever found that shows it. I am not sure the original source, but one of the 1.6L TBI vehicles.
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