Hi, our S80 has gone into limp mode with a "reduced engine performance" message a couple times this week. There are no CEL codes, and disconnecting the battery for 10-15 min resolves the problem for awhile. The first time it happened, after reconnecting the battery, I was able to drive it about 20 miles home with no issues. The next morning when we started the car, the message was back. Again no CEL codes... disconnected battery again, reconnected, and message gone, but haven't driven it since.

Here's a bit more history on the car for context. We just got it from family last week, so all of what I list below happened before that. About a year ago, the rear view mirror fell off, was just dangling by the wires. Their european auto shop told them they couldn't fix it properly, so they went to the dealer, who quoted them $450 to repair. They decided it wasn't worth it and just put a generic mirror up there after cutting the wires and tucking them up under the roof fabric. The old mirror was thrown in the trash (not sure how much of a problem that causes if a new factory mirror is required, as I think the car computer is programmed to the board inside the old mirror).

Since cutting those wires, they've gotten random false messages like tire pressure, CEL, etc, which they concluded were due to mirror wires being cut. It subsequently passed emissions like that. A few weeks ago, they started getting an "engine system service urgent" message. Then the "reduced engine performance" issue I described above began after we got it last week.

Aside from when it goes into limp mode, the car runs smooth... no lack of acceleration, no obvious misfires, etc.

Any thoughts on whether the limp mode issue could be related to the mirror issue? thoughts on a solution? Assuming the limp mode is unrelated to the mirror, we'd be ok at least for now with the random messages coming up so long as there aren't mechanical problems and it can pass emissions... we'd just want to focus on the limp mode issue right now.

Thanks in advance.

 

have you measured your system voltage during one of these events? Its plausible that the alternator is dropping out and you have a weak battery.. easy enough to test.

 

I don't have a voltmeter, but would the voltage drop only occur momentarily, or would it remain low while the car is in limp mode? ie, would it need to be tested while driving?

As an alternative, could I just get my battery tested at the auto parts store? If the battery is good, would that eliminate this as a potential cause?

I'm thinking about digging out those mirror wires from behind the fabric and twisting/capping them together to complete that circuit. Seems one potential cause could be shorts and disconnected wiring. Thoughts on this? Any potential harm? or hope?

 

a trip to Harbor Freight can get you a VOM for about $20. It can't hurt to have a store measure the battery as a baseline, but that won't tell you if the alternator is dropping out intermittantly (say due to an issue within the regulator). These days its not a bad idea to own your own volt meter and a OBD2 reader (being a nice dad, I gave my son a $30 unit for Xmas - again from HF and its already come in handy on his S40). $50 and you'd have some useful self diagnostic tools.

 

hello did you ever find the cause to this issue, I have the same issue on my XC90 D5

 

sorry I didn’t see this sooner. I haven’t gotten it resolved… been dragging my feet on it, but back on the case. Would be interested to hear if you found the cause.

I just spoke to a friend of a friend Volvo mechanic, and from my description he thinks there are 2 independent issues.

One is the mirror, which is a module that controls the locking system and TPMS… perhaps the reason for the random light previously.

He thinks the other issue causing limp mode is likely needing a PCV box, throttle body, and maybe wiring connectors to the main computer.

i asked if a short in the system could be causing limp mode, and he said yes, but also seemed to be saying no avoiding the pcv box and throttle body work… waiting for clarification on that.

I’m assuming PCV box means breather box, which from my research seems different from PCV breather system… would welcome some clarification on that. Either way, the suggested work seems like a dealer might charge almost as much as the car is worth in good condition.

This guy can’t work on it anytime soon, so I might bring it to a dealer for diagnostic. I’m seeing complementary diagnostics through “My Volvo Experience”… anyone know if that applies to all Volvos, orig owner or not?