Hi community, I'm having Volvo s80 2001 with B5204T5 engineI have 5 cylinder slots, each with its coil and connector. I got a cylinder 5 misfiring code and after checking, it seems that coil number 5 is faulty and needs replacement. However, when I tried using the coil from cylinder 1 in the slot for cylinder 5, it didn't work. I then tested the original coil from cylinder 1 in slots 2, 3, and 5, and it worked fine. Now, neither cylinder 1 nor 5 works, even with new coils.

It appears that cylinders 1 and 5 are not firing, even with functioning coils. What's strange is that the coil pack for cylinder 1 was working perfectly fine before.

I checked the voltage output of connectors 1 and 5, and they showed 14 volts between the power wire and ground (Key ON and when engine running).
When I tested the trigger wire of both connectors 1 and 5 against ground, it read 0.33 volts. The same reading was obtained for cylinders 2, 3, and 4, which are working normally. My ECU model is Bosch 08627456A.

Is there a possibility that cylinders 1 and 5 are triggered by the same line, and if so, could that line be faulty?
Would I need a new ECU?
As for fixing it myself before taking it to a dealership, is it safe to drive 100 kilometers with only 3 cylinders working (with the injector connectors for cylinders 1 and 5 disconnected)?

 

I had that same issue a couple months ago in my 2006 S80 T5.
It was showing random misfires on a couple differant cylinders and it turned out to be an issue with the Crankshaft Position Sensor even though it wasn't throwing
a code for that.
Some one else here on the forum had that same issue and thats how I found out about it so I went to the junk yard and grabbed a sensor put it in mine and problem solved..

 

assume you have scanned for all stored codes? Have you pulled the plugs to see what they look like? Is the car consuming any oil or coolant? I'd inspect the wire harness to the coils to check for any cracked insulation, cracks in the connectors etc. After that, you may want to throw some injector cleaner (or run a few tankfuls of 93 octane (US) brand name premium to see if that helps. Finally you may need to do a compression test to see if something is different about those two cylinders.

 

Hi, Thanks everyone for the replies. @rpalme @mt6127
I finally identified the problem.
It appears that the ignition coil for cylinder number 5 was indeed faulty. Upon further inspection, I found that the ignition power connectors for cylinders 1 and 5 were working, but the "phase" signal was not coming from the ECU. Fortunately, I had an old ECU on hand, which I replaced with the new one due to cold start and false alarm issues. When I tried the old ECU, all the cylinders started firing and working properly. Additionally, I replaced the ignition coil for cylinder 5. Now the car runs smoothly.

It seems that allowing the ignition coil to spark outside the engine, possibly to visually inspect the spark, may have caused the ECU to shut off the pins or damage them at the PCB level. As a result, I've sent the ECU for repair to determine the exact issue.

The lesson learned here is to never allow the ignition coil to fire outside the engine, as it can lead to unforeseen complications.