XC90 intermittent engine light

MrEire · Post by **MrEire** » 08 Dec 2019, 19:49

Hi All,

I just recently purchased a 2007 XC90 3.2L, Drove it 600 miles this weekend and about 100 miles into the road trip a check engine light came on

The car is running fine with no noticeable difference with the engine light on, not misfiring, low on power etc.

I stopped by O Riley's and got it plugged in just to be sure, a few codes came back.

P0420 Catalyst system efficiency below threshold (Bank 1)
P0088 Fuel Rail/ System Pressure - Too High
P0505 Idle Air Control System - Algorithm based Failures
P0012 Intake Camshaft postion timing - over-retarded (Bank 1)
P0737 TCM engine Speed Output Circuit

I switched the car off at O Rileys when I was getting it checked out and when I started it back up again the engine light went off (They didn't clear the codes), drove it another 200 miles and the engine light remained off. Drove it back today and stopped about 100 miles into the trip and engine light came on, turned the car off and back on again which made the engine light remain off for the remaining 200 miles.

Any help would be appreciated as to where to start diagnosing! My thought was a possible 02 sensor? I checked the plugs at the side of the road and they are all fine.

Thanks!

Masscomguru · Post by **Masscomguru** » 09 Dec 2019, 04:35

Check the battery and charging system. Low voltage really messes with these things.

MrEire · Post by **MrEire** » 09 Dec 2019, 11:09

Battery is fine, it's at 12.72v. It is also charging under load at 14v not underload it's at 14.3v

Post by **oragex** » 09 Dec 2019, 13:36

I have the same on mine. It's a damaged catalytic converter. Basically, the efficiency of the converter is right at the limit of the downstream O2 sensor, so it triggers the light depending on the driving conditions. Mine started to turn on especially in hot days, but got more steady as the miles kept piling up. I know well because I know how the converter got damaged (my mistake). I recommend finding first the reason why the converter started to fail - this is almost always an ignition problem. Because if you replace the converter and the gas mixture is still not burned properly, the new converter will also fail. Try see if the spark plugs, ignition coils (at least 1-2 of them), and thermostat were already replaced. Well possible a previous owner drove with faulty coils, throwing unburnt gas into the converter - kaput.

MrEire · Post by **MrEire** » 13 Dec 2019, 10:05

Interesting! I just checked the service records, the plugs were replaced at 150k and the thermostat was replaced also due to being faulty so I think you're correct. I'll take it to an exhaust place and see if they can do a back pressure test on the converter. The wife has been driving it this past week with no sign of the engine light returning.

Thanks for the help!