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Immobilizer question Topic is solved

Help, Advice and DIY Tutorials on Volvo's P80 platform cars -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, including 850 R, 850 T-5R, 850 T-5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

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subzerocarfanatic
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Re: Immobilizer question

Post by subzerocarfanatic »

I was wondering that abscate but was not sure how to find out yet if that is the culprit. I used an Autel Maxi Pro MP808 scan tool last night anyway i found some codes I do not understand some of them. I charged the battery on trickle charge all night because the test pulled the battery down just a bit yesterday. I will post the codes and see if anyone might understand them better than I can.
I used to remove the battery cable each time before starting the car and that worked but found that removing the ignition fuse done the same trick and was easier and faster.

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Post by subzerocarfanatic »

I forgot to mention, last night while running the autel scan tool in diagnostic mode to check engine/ ECM codes if there was any, I had to do the same fuse pull trick so the Autel would communicate with the ECM, it would not communicate with the ECM until I turned the key off, pulled the fuse re-installed the fuse then turned the key on, then the scan tool would communicate with the ECM. I will see if I can post an image

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Post by abscate »

abscate wrote: 06 Dec 2021, 18:01 Where’s the electrical on that? Does it push in the pin on the electrical part of the switch? There are no electricals on the tumbler assembly
Scrubbing bad information from the internet.

Inserting the key pushes a plunger on the key tumbler which pushes in a pin on the ignition switch electrical part, on the left side of steering column,

When this pin is depressed, after counseling, it connects terminal 30 to terminal S on the ignition switch. This runs to the chime, which is grounded when the driver door is open, via the door lock module.

The antenna ring plays no role in mechanical key detection.
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Post by subzerocarfanatic »

abscate wrote: 08 Dec 2021, 06:08 This isn’t an antenna ring problem. Pulling that fuse is probably doing an ECU reset which helps the starting sequence.

If cranking is inhibited on a 1999 or 2000 car, your light control module , 2/76 is not grounding your starter relay. It does this under microprocessor control , not a simple thing to diagnose.

If it cranks, starts, stalls…that’s a bad key signal.
By starter relay, I assume that is the blue one in the main fuse box ( on shock tower LHD). I guess I need to figure out what and where 2/76 is and see what could be causing it to not ground. Any ideas?

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Post by abscate »

That’s a horrible rabbit hole on the 2/76 module. One way around it is to ground the 85 terminal on the starter relay directly to a chassis ground with wire surgery

The four relays in the kidney fuse box are , from left side of car to right

Main engine
Air pump ( usually empty on 99-00)
Starter relay
Air conditioner compressor ( smaller than others)

More thoughts. From deep in the memory banks, I recall your HPT C70 is indeed an M56 standard shift

:D :D :D :D :D

Speculation. The clutch switch on these cars connects directly to the ECU on these cars, logic in/out. Mystery solved as to why the starter relay grounds through 2/76. The ECU has to tell the 2/76 to ground the starter relay under condition of clutch pedal depressed.
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Post by subzerocarfanatic »

abscate wrote: 10 Dec 2021, 03:50 That’s a horrible rabbit hole on the 2/76 module. One way around it is to ground the 85 terminal on the starter relay directly to a chassis ground with wire surgery

The four relays in the kidney fuse box are , from left side of car to right

Main engine
Air pump ( usually empty on 99-00)
Starter relay
Air conditioner compressor ( smaller than others)

More thoughts. From deep in the memory banks, I recall your HPT C70 is indeed an M56 standard shift

:D :D :D :D :D

Speculation. The clutch switch on these cars connects directly to the ECU on these cars, logic in/out. Mystery solved as to why the starter relay grounds through 2/76. The ECU has to tell the 2/76 to ground the starter relay under condition of clutch pedal depressed.
So you think maybe the clutch switch might be causing an issue? I wonder if it has some sort of switch like the gas pedal does, some sort of potentiometer, that can go bad like the one on the accelerator pedal. What module is the 2/76? I need to look at a wiring diagram I guess if I can find one, not the best at understanding every aspect of wiring schematics hopefully enough to understand it though.
I found an old Xemodex diagnostic flow chart, I know it is for the ETM issues but might help me some Because when the key is turned on the ETM dash check light does not come on before starting it like it should ( unless the ignition related fuse is pulled then reinserted) as mentioned earlier. The ETM is supposed to make a high pitched tone or whine for 6 seconds and make a clicking sound from the butterfly opening when the key is turned on before starting, well if I pull the fuse first everything functions properly, if I do not pull the fuse the ETM will click but the high pitch tone is constant, not just for 6 seconds, so if it is the ECM or a bad 2/76 relay ground or whatever I have been trying to figure this out for quite some time. Yes you are correct HPT 2.3 with M56 5 speed. If taking it to Volvo was an option I would but I do not have a Volvo dealer unless I drive over 400 miles 1 way.
If you or anyone on here can help me try and trouble shoot this and narrow it down I would be so appreciative. I would gladly make a donation to the forum, I know that is not why you or others on here help but it would make me feel better if I at least contributed something.
20211210_163235.jpg

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Post by subzerocarfanatic »

I will check the chassis grounds, that I can recall there are 4 maybe more, one behind each headlamp area, one on left shock tower one on front side of engine block, not sure if there are more. Not sure if you remember abscate about a year ago when I was having the issue of the car stalling every time I hit bumps or drive over cattle guard ramp before getting on interstate, anyway that was fixed, it was a loose chassis ground behind passenger side headlamp, it was very hard to find.

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Post by abscate »

I’ve documented both the turn in dash light sequence and the clutch switch measurements in this forum for the ME7 1999,2000 cars. I’ll try to find links and post up
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Post by subzerocarfanatic »

So far I have not found any loose chassis ground. Still looking and praying I can figure this gremlin out. It has to be something simple because the car starts and runs fine as long as I pull the Ignition fuse each time before starting, but who wants to do that every time. (

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Post by wizechatmgr »

subzerocarfanatic wrote: 13 Dec 2021, 14:45 So far I have not found any loose chassis ground. Still looking and praying I can figure this gremlin out. It has to be something simple because the car starts and runs fine as long as I pull the Ignition fuse each time before starting, but who wants to do that every time. (
If you leave the key in the ignition and open the door, does your key reminder chime 'chime'?
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