2000 V70 XC Odd intermittent hesitation and electrical quirk

[ZX2Fast]

2000 V70XC LPT 2.4 195,000 miles.

I'm wondering if this car needs back pressure to function properly. I removed the two mufflers at the back (sounds beastly) and took it for a drive. Sometimes (not all the time) when I floor it, (or more than half-throttle) it'll cut out (acts like it is running lean or misfiring, no CEL flashing) for a moment or two and then continue accelerating. The only thing I did besides cutting the mufflers off is run wiring for the tow hitch and trailer brake controller. I don't have the maintenance history for this car but it appears it was always done at the dealer. Even the battery is a Volvo brand. So, I don't know how old the spark plugs and fuel filter are. It could need a tune-up but it is odd it acts like this right after I cut the mufflers off. I do have a front O2 sensor code (still waiting on the part) but the car had that code when I bought it and it didn't cut out like this.

I'm also experiencing an issue with the headlights. I think the relay is bad. It was intermittent and pushing the relay down would restore the headlights (and blinkers, reverse lights, seat belt warning, rear foglight) and then it stopped completely. It looks like a standard Bosch 5-pin but it doesn't act like one. I had a Bosch 5-pin on hand so I plugged that in and the headlights wouldn't work at all, though the parking lights would work only in the parking light switch position. I took the ACC relay (runs the radio, blower) and put it in the headlight spot and that works, though I can't seem to turn them off when the key is on. No matter the switch position, the headlights are on (except in parking only) when the key is on. The Bosch 5-pin went into the ACC spot and I have all interior functions except for power windows. Is there an off-the-shelf option for this relay or am I going to have to order a Volvo relay?

EDIT: I restored normal function to the ACC circuit by swapping the Bosch 5-pin with the starter relay. The starter works normally so it appears my issue is solved. I will be looking to get the Volvo relay to put back in the starter position just for OCD sake.

[rspi]

Not sure about your muffler situation but the head light relay is a double relay and is usually grey.

[ZX2Fast]

The headlight relay hasn't failed. The relay that powers all the circuits I mentioned (headlight switch, reverse lights, seat belt chime, rear fog light, etc., that has failed. I needed to know if that relay (appears to be a Bosch 5-pin) is special for Volvo because it doesn't behave like a Bosch 5-pin and the Bosch relay I used wouldn't function and it is a known-good relay. Anyways, I took the 'starter' relay and swapped it with the failed relay and it works as it should. I put the Bosch 5-pin in the 'starter' position and the starter works.

[mikealder]

Try swapping 105 with 106 and see if the fault migrates between X supply and 15L supply control :

Relays in the central electrical unit



101 - 102 Control Module, Cruse control (4/3) (FENIX)
103 Relay fuel pump (FP) (2/23) (Not MSA)
104 - 108 Headlamp relay with bulb failure warning sensor (2/1)
105 Overload relay X supply (2/30)
106 Overload relay 15I supply (2/6)
201 Fog lamp relay (2/2)
202 Relay alarm horn (2/77)
203 Intermittent wiper relay (2/4)
204 Intermittent relay tailgate wiper (2/16) (S70/V70) or Audible signal softop (7/117) (CONV)
205 Relay rear hatch opening (2/67) (CONV)
206 Relay window lift mechanisms left-hand side (2/99) (CONV)
208 Relay heated rear windshield/ door mirrors (2/44)
210 Relay window lift mechanism right-hand side (2/100) (CONV)
212 Relay seat belt reminder/ key warning (2/5)
214 Automatic fuses 11C41-42 (CONV)