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Discussion Starter · #1 ·
Hello all,

I just ran VIDA on my XC90 V8 and got the codes in the picture. Is it really possible to have 7 misfires at a time? I am getting ready to buy plugs and coils and wanted to get your opinion first. It has 166K miles.
Also any idea about the TCM code?

Thank you in advance.

 

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ECM was not at all happy with something internal software if those codes are legit. And for all the codes, go to history and see how many cycles with and without the error, etc. See if all the misfires came at the same time as well as any other codes correlating to something common.

Is the car running? What brought you to look at the codes?

If the car is running, after looking at history I might erase all the codes and see that the codes are erased. Then I would turn the car off, wait 5 minutes or more, and disconnect the battery and after 1/2 hour or so reconnect it back up following the normal procedures. After that, I would drive the car and see what comes back.

My 5 cents.

*VIDA does mention something about "Poorly charged battery or corroded connecting wiring" as a possible cause with the ECM errors, probably ought to check both of them, if only to omit.
 

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Here's what I do:
Print the codes to a PDF file and save them (VIDA has a print function. I write the date and odometer reading in the filename for reference)
Clear all codes.
Go for a drive of 5min or so so you have a complete drive cycle done. Or just drive the car normally for a couple of days.
Look at codes again, record them!
No need to disconnect battery.

Report back with what you find afterwards
 

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I had misfire issue along with intermittent rough idling and sometimes the "Try Slow Down or Shift Up" message.

Replaced the plugs but it didn’t help. I was about to replace the coils, but due to cost, I held off and replaced the crank position sensor instead.

The new crank position sensor solved my above issues. Cost a lot less, about 1/8 compare to replacing all the coils, and was the root cause for the my misfires.
 

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How does the car run at idle and under acceleration? I recently purchased my 06 V8, and it threw a cylinder 4 misfire during the test-drive. I had the dealer read and clear it, figuring it was a simple coil change. In the following week I felt the intermittent misfire become more frequent, to where I could tell it was missing every firing. Acceleration was rough, and I would typically see the "Slow Down or Speed Up" message. Plus, some mornings she would stall just a few seconds after firing up the first time.

When I finally got a chance to read codes it looked similar to this. Seven misfiring cylinders, and the random misfire code (none of the other stuff you have though). I bought 8 new plugs (since it is a new-to-me with 165k miles) and a coil. While doing the plugs I could tell that number 4 hadn't been firing (I can show you a picture if you're curious) so I put the new coil in 4. Of course I had a hunch this was the problem child from my test-drive. 1 month later no misfire codes have re-appeared, and she's running great.

So my recommendation to you is similar to what has already been said. Save the list of codes (or just keep the photo in a safe place) then clear them. Start the car and let it run for a few minutes, then see what comes back. In my case, it appears one bad coil caused behavior that resulted in misfire codes for 7 cylinders.
 

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Discussion Starter · #6 · (Edited)
Hello all,
I replaced the spark plugs with OEM spar plugs and bought 8 used Volvo ignition coils that came with one year warranty and installed them yesterday. The check engine light came on and after some certain speed, the left message location says shift up or down and check engine light would blink. I scanned the car twice and got the codes below this time. I think the misfire issues still persists, any idea what could be the problem now? The four of the eight coils are bad? I'd appreciate any input. Thank you all.

 

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Discussion Starter · #7 · (Edited)
If you guys think I need to replace the coils, would they be Cylinders 2-3-5-8? I got the cylinders order by numbers online but named them by logic.


 

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Go into one of the codes and select Fault tracing.

Couple interesting statements in there, one being common to your specific set of cylinder codes- For ignition coils cylinder 2, 3, 5 and 8: control module terminal #A62 (#B2) and relevant ignition coil terminal #2.

Can start there and see how far you get.

* Solid black wire, pin 2 each coil pack for 2,3,5,8- central junction point 53/360 before it goes to ECU pin A62. Solid red wire, pin 2 each coil pack for 1,4,6,7- central junction point 53/358 before it goes to ECU pin A64.
 

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Short version troubleshooting might be to remove all the coil pack connectors off and do a continuity check between pins 2/4 and 2/3 for each, should be open (infinity or super high value for resistance). If for some reason you get any zero or low resistance (short) values, consider removing the ECM connectors and perform the test again to omit the ECM itself as a cause. VIDA does not explicitly suggest to disconnect the battery before removing the connectors but I might do that just to be safe.

As well, if you can find a wiring diagram it'll help in seeing the wire paths. Cylinders 2,3,5,8 and 1,4,6,7 each have a junction point (53/359, 53/360) where the four coil pack misfire wires merge into a single conductor that runs to the ECM (A62/A62).

Misfire signal is noted as pulse width modulation (PWM) input at the ECM so not easy to measure unless you have a waveform monitor (like an oscilloscope).

Good luck with your troubleshooting.
 

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Discussion Starter · #11 ·
I found the wiring diagram, thanks to SwissXC90.
I will be checking the continuity of the pins as you suggested and report back by the end of this week.
Thanks again.

 

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"The engine control module (ECM) regulates the ignition coils and checks their function via a separate diagnostic cable. The diagnostic trouble code is generated if the control module detects that the signal for an ignition coil is faulty. "

Interesting when you go look for this wire, it's noted as applicable to non-turbo models only. Sensor wire definition I believe is IGf (produced by the coil pack itself on successful firing).

While there's not anything easily located to describe the function of Volvo's implementation of the sensor wire, it's discussed for some other manufacturers here (see 4-wire section)- https://opensiuc.lib.siu.edu/cgi/viewcontent.cgi?article=1025&context=auto_pres
 

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Discussion Starter · #13 ·
I was able to find the issue over the weekend. I started checking all four ground connections and gently pulled to see if they are tightly connected and the one near cylinder 4 wasn't intact even though it looked intact. I reworked the connections and solved the issue.

So here is my advice to anybody going through a misfire issue. If you ever get a misfire issue with bunch of misfiring cylinders, first check ground connections and don't spend your money right away with replacing all spark plugs and coils :)
 
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