Fluctuating idle/dead gauge cluster

Post by **subzerocarfanatic** » 24 Aug 2024, 21:45

Hello everyone, it has been a while since I have had any issues with the C70 but here I am again. I drive it a couple times a month just to keep it alive and circulate the fluids, I never resolved the no start issue, so each time I would drive it I would have to pull the 15 amp fuse in the kidney shaped fuse box under the hood on the drivers shock tower area, and reinsert the fuse and it would start and run just fine, we have been doing that for the past 2 years or so. I went to crank it today and it did start but I noticed the clock was wrong, the tachometer was not working, it was on 0RPM. After a very short time it started the up and down idling like I was tapping the gas pedal briefly and letting off, at this point I could press the gas and rev the engine up.
I killed it tried 5 or 6 times to re-start it and it would not start, eventually I got it running again with the same erratic idling, tach still not working, only now there was no response at all when I pressed the gas pedal, I could hold it to the floor and no response.
I finally managed to get it running and drove it up in the driveway, pulled the battery and it is on a all night charge on my NICO charger because the battery was under 12 volts after all this. Though I never figured out why I had to pull the 15 amp fuse out and reinsert it every time to be able to start it, we still have been able to drive it the past 2 or 3 years by pulling the fuse each time as mentioned and it has ran ok, so why this now all of a sudden, my 1st thoughts were the ETM ( electronic throttle module) but why would that make the tachometer not work, does not make sense to me. Could it be a bad coil or coil wire plug or MAF sensor, these could affect idling but the tach not working is confusing.
Once I install the battery tomorrow I will start looking around and see what I can find. This forum has been a life saver for me over the years since owning this car so I thought I would come here for help and any thoughts anyone might have.

Post by **abscate** » 25 Aug 2024, 04:29

It sounds like a combination of both low bus voltage and a failing ETM , but that’s a complex set of symptoms

Borrow, beg, or buy a new battery to start. A bad battery , thst might still crank the car fine, will spawn a host of issues

My 99 v70 with a 5% state of charge battery would light up dash lights and ABS when I flashed the headlights , for instance.

Post by **packetfire** » 25 Aug 2024, 13:25

a) Which fuse (by number) do you pull? Could this be the engine compartment fuse that supplies power to the CEM?

b) Once you get a solid source of 12 volts attached, consider the ground connections for the CEM, DIM, and ETM. Grounding can cause the widespread insanity you are seeing, but so can corrosion and the resulting poor connections in the CEM when the sunroof drains clog and drip on the CEM.

Post by **subzerocarfanatic** » 25 Aug 2024, 22:29

Ok, the battery is an AGM battery so it charges at a lower and slower rate so it charged all night, I put it in today and the car started right up and the tachometer was working and the accelerator pedal was functioning normal and no fluctuating idle. I have never seen a car have so many different symptoms just from a low battery. I will take a picture of the mentioned fuse in the kidney shaped fuse box in engine bay that I mentioned I have to pull and reinsert every time before I can start the car. What I would give to fix the issue that causes me to have to pull the fuse every time before I start it, it's related to ignition I believe and the ETM. If I do not pull the fuse before trying to start each time after the ignition has been turned off the ETM check light on the dash that comes on a few seconds every time before the car starts will not light up and do its check before starting, once i remove and reinstall the fuse then the ETM dash light comes on briefly as it is supposed to then the car will start.

Post by **MoVolvos** » 26 Aug 2024, 12:04

abscate wrote: ↑25 Aug 2024, 04:29 It sounds like a combination of both low bus voltage and a failing ETM , but that’s a complex set of symptoms

Borrow, beg, or buy a new battery to start. A bad battery , thst might still crank the car fine, will spawn a host of issues

My 99 v70 with a 5% state of charge battery would light up dash lights and ABS when I flashed the headlights , for instance.

subzerocarfanatic wrote: ↑25 Aug 2024, 22:29 Ok, the battery is an AGM battery so it charges at a lower and slower rate so it charged all night, I put it in today and the car started right up and the tachometer was working and the accelerator pedal was functioning normal and no fluctuating idle. I have never seen a car have so many different symptoms just from a low battery. I will take a picture of the mentioned fuse in the kidney shaped fuse box in engine bay that I mentioned I have to pull and reinsert every time before I can start the car. What I would give to fix the issue that causes me to have to pull the fuse every time before I start it, it's related to ignition I believe and the ETM. If I do not pull the fuse before trying to start each time after the ignition has been turned off the ETM check light on the dash that comes on a few seconds every time before the car starts will not light up and do its check before starting, once i remove and reinstall the fuse then the ETM dash light comes on briefly as it is supposed to then the car will start.

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Next, per recommendation check the ETM. Clean and if it improves or back to normal, it's either dirty or starting to fail.
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Daveh69 · Post by **Daveh69** » 26 Aug 2024, 15:19

X2 on the grounds ,,, engine and chassis,, check them all

Post by **subzerocarfanatic** » 26 Aug 2024, 21:06

I will check the ETM butterfly plate, I doubt it is dirty, the car has only been driven probably less than 1000 miles in the last 3 to 4 years. When I originally installed it in 2019-2020 it was because the original white sticker ETM model 9186793 had failed, it was the original one, so the one that is in there now is a used one from eBay that I installed 4 or 5 years ago but it was a unit with a XEMODEX sticker on it so I figured those don't ever fail so it did not matter if it was used, it was rebuilt in 2013 If I remember correctly is what the listing said when I purchased it back then. Why it will only run when the fuse is pulled then reinserted I do not understand but it works every time , it is a bit of a pain to have to do every single time I go to start it though. Once the car has been started and then shut off the fuse has to be pulled and reinserted afterwards before the car will run again. Weird...

Post by **MoVolvos** » 26 Aug 2024, 21:31

subzerocarfanatic wrote: ↑26 Aug 2024, 21:06 I will check the ETM butterfly plate, I doubt it is dirty, the car has only been driven probably less than 1000 miles in the last 3 to 4 years. When I originally installed it in 2019-2020 it was because the original white sticker ETM model 9186793 had failed, it was the original one, so the one that is in there now is a used one from eBay that I installed 4 or 5 years ago but it was a unit with a XEMODEX sticker on it so I figured those don't ever fail so it did not matter if it was used, it was rebuilt in 2013 If I remember correctly is what the listing said when I purchased it back then. Why it will only run when the fuse is pulled then reinserted I do not understand but it works every time , it is a bit of a pain to have to do every single time I go to start it though. Once the car has been started and then shut off the fuse has to be pulled and reinserted afterwards before the car will run again. Weird...

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If all else fails connect 2 wire to the fuse pins and extend to the interior of the car. Set up another fuse box under the dash and add a toggle switch in one of the blanks in the dash and that becomes your start safety switch.
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