Sorry in advance for the length, but I wanted to include all the details to see if someone can help me figure out the possible issue(s) here or even help me find the likely electronic issue that could cause this weird combination of symptoms.

2004 Volvo XC90 T6:

• We don't drive this car very often and it's been in the 20s overnight here recently
• Went to start it a few days ago and it would crank strongly - it actually started twice but then immediately died
• I put it on a battery charger to make sure the battery was as strong as possible while I tried to find the issue - the battery is not in great shape due to so much inactivity during the pandemic, etc
• I did see code P0073 once or twice while working on it and cleared it with my ScanGauge - the temperature on the dash aligns with the actual air temp and I've seen no other codes throughout this process
• I didn't notice this until later, but the gear indicator in the instrument cluster only showed a dash, and the orange lights by the gear selector have not been coming on
• Oddly, the turn signals also are not flashing when the alarm is armed - the siren has been bad on this car for years and it has a persistent "Alarm system service required" message, but we've never had any issues like this in the years that's been the case - we just don't need the alarm so I didn't bother to fix it. The lights do work fine with either the flasher or the turn signals (Edit: I figured out eventually this is unrelated - the turn signals don't flash when the hood is open apparently, and I had it open most of the time I was troubleshooting things...I guess that means the fob will lock the doors with the hood open but isn't really arming the alarm...)
• I tried resetting the alarm by locking and unlocking the car multiple times with both the key fob and the key itself with no change
• I checked all the fuses and relays, swapped a few relays, etc., with no effect
• There seemed to be some initial/residual pressure in the fuel rail, but it would only let a small amount of fuel out through the valve and the pump would not come on, so I'm pretty sure the fuel pump isn't turning on properly but I'm not sure if that's due to the pump itself or something in the electronics telling it not to run. The fact that I also don't have gear indicators makes me think it's not a problem with the actual pump. I have not tried to find and check the PEM yet - is that at all related to the gear indicator?
• I do think the fuel pump would run when I first tried to start the car and it started but for only a few seconds - it's hard to remember after so many other tries, but I think I heard an extended pump running sound when I first turned the key but then two starts without it staying running...
• I looked up a lot of things and one thing I tried was the relays in the cargo compartment - no changes checking them, swapping them, etc.
• As a long shot, I looked up all those fuses and the only one that seemed to not be a courtesy-type of circuit was Fuse 17 (AWD Control Module) Just to see, I pulled it out and tried starting the engine, and it fired right up! That's when I noticed the P gear indicator and realized it wasn't there during all my other troubleshooting
• The car seemed to run fine, and replacing the fuse I'd removed didn't cause any issues.
• Stopping and restarting the engine also worked fine
• The "Anti-skid temporarily off" message appeared but went away after driving a mile or so
• I drove the car for some errands to really test it, and it acted totally normal again. The turn signals flashed when the car was locked with the remote, the gear indicator was there, and there were no error messages other than the alarm system one that had been there for years
• I assumed pulling that fuse reset something between the ECUs and this was some type of transient problem caused by a combination of cold and perhaps low batter voltage
• Now it's a few days later, about 45 degrees out, and I went to start the car again - same issue: I heard a long pump noise when I turned the key, looked for the gear indicator and only saw a dash, and the car started but died right away. It started a second time but died right away, so I'm back to where I was a few days ago
• I assumed the same thing with the AWD Control Module fuse would work again, but no luck this time...I've tried pulling and replacing that fuse under all conditions (key off, key in run, etc.) and no luck - I've yet to see the gear indicator again and I know it won't start until I see that!
• I checked every single fuse again with a continuity tester and the only one I found that was burned out was for the alarm - I thought maybe I was an idiot and that had been the issue all along with that warning light! Unfortunately, replacing that fuse didn't change anything - still no start, same alarm message, and turn signals don't flash when locking the car with the remote
• All the other fuses are fine
• Gas cap is tight
• I disconnected the battery for at least 15 minutes but no changes...
• The only other issue with the car is the sunroof doesn't work - we don't use it often enough for me to mess with it and the fuse to the upper control module is fine
• Nothing obvious around the shifter - I pulled the bezel to see if something was disconnected there but all looked fine
• Fuel pressure still seems absent - I get a little to run out if I open the valve on the rail, but nothing after that and the pump isn't turning on
• The fuel pump isn't as old as the car - we had a fuel smell a few years ago and the dealer performed a recall on the fuel pump that fixed that issue
• Admittedly, the battery wasn't as strong today as it was when I got the car to start finally the other day, so I do think it's possible this is all voltage-related...I'm charging the battery again now to test that theory. Jumping the car from another car doesn't seem to help

Does anyone know of a possible common cause that would prevent the fuel pump from running and involve:

• the ability of the alarm module to flash the turn signals (signals work otherwise) (Edit: I figured out eventually this is unrelated - the turn signals don't flash when the hood is open apparently, and I had it open most of the time I was troubleshooting things...I guess that means the fob will lock the doors with the hood open but isn't really arming the alarm...)
• the gear indicator on the dashboard and lights by the shifter
• the power to the AWD control module
• code P0073 - I had to replace the outside temp sensor last year as the dash temp was way off, and I think I remember that the sensor in one mirror is for that display (and maybe the HVAC automation) and the sensor in the other mirror is for the actual engine ECU. It's possible I know that because I replaced the wrong one last time, so that sensor might be less than a year old too. This seems like a good possibility since maybe the ECU won't let the fuel pump run if it has no idea how hot or cold the ambient air...the main reason I'm skeptical of this, though, is the gear indicator and alarm/turn signal issues...seems very weird that a bad temp sensor in a mirror would cause all of that! Also, ambient air temp doesn't seem like a critical enough input for the engine ECU to not allow a start - I think engines are pretty tolerant of any air/fuel ratio issues caused by that and you'd think it would just use a default mixture setting if the temp input was out of range... Occasionally when it's really cold, we'll get the code for "coolant temp out of range" or something like that, which has always gone away in a few minutes and has never caused any starting or running issues - I've always attributed that to the coolant being out of range on the low end after a start when the car was sitting in very cold temperatures...the fact that it would still start and run with that code makes me pretty skeptical that the ambient air temp sensor would prevent the engine from starting!

Thanks in advance for any ideas!

Olivier

 

I was out of town for a few days and it was on the trickle charger until I just got back. It's still about 37 degrees, so about the same as last time. With a topped-off battery, the gear indicator in the dashboard was back as were the lights by the gear selector, and I also heard a long hum from the fuel pump priming. It wouldn't start right away, though, and the message window said things like "Reduced Engine Performance" and something like "Engine System Service Required" (I don't remember the exact wording but it seemed to indicate the main ECU was done) among a few other messages like "Anti-skid Service required". The turn signals still would not flash arming the alarm, but I finally figured out that's unrelated - it was because I didn't have the hood fully latched because the trickle charger was still connected! Once I removed the fuse to the AWD control module, the engine fired right up, same as before, and the only new message is the "DSTC temporarily off" message that I expect will go away in a mile or two as it did last time. I guess the battery is definitely toast and the lower voltage is somehow causing all sorts of ECU issues and interactions, including something that requires the AWD control module to be reset for some reason. It's strange since the battery has plenty of volts and amps to crank the engine strongly and run just about everything in the car except the ecu that drives the gear indicators and lights that I guess are required to allow the fuel pump to run. There might still be an interaction between the pretty low temperatures and the voltage issues - I'll see when it gets warmer and whether the P0073 code persists.

 

Having similar problems with my ‘05 - keep me posted

 

Same problem on 2004 v70 . use the car once a month on my trips to the Florida house . It is now the end of Feb / did you fix the problem ???

 

It was the battery...replaced it and everything is normal again. I've never had a battery that had enough power left to crank the engine (a lot), but issues running electronics, etc. After replacing the batter, the P0073 code also hasn't appeared again either.