Engine System Service Required + Check Engine Light

[WellingtonX]

This topic relates to my 2005 XC90 2.5L AWD with 140,000 km. I keep thinking that I have fixed this problem but it eventually comes back with the Engine System Service Required + Check Engine Light illuminating on the dash. The alerts will clear themselves after random periods but come back.

I took the car to a mechanic with the Volvo DICE system to read the codes this week. The first scan listed a codes but none were active. He cleared the codes and we drove it for a hour before the alerts came on the dash again. Interestingly, I was stationary and then turned onto a main road and had to accelerate a little more than normal and the alerts came on. Back to the mechanic and scan found the following codes:

CCM-0040 Air quality sensor internal fault, - ACTIVE
ECM-1210 Mass air flow sensor-Flow too high - ACTIVE
ECM-212C Long Term fuel trim, bank 1 - Signal too high - NOT ACTIVE
ECM-216C Long Term fuel trim bank 1 - Signal too high - ACTIVE

Was advised by mechanic that CCM-0040 was a fault with the cabin fan and not to worry about that. I had seen the ECM codes before and replaced the MAF and the front O2 sensor with Bosch items several months ago. The mechanic believed that the codes were indicative of a vacuum leak but could not find any issues with a visual inspection. I had previously suspected a leak from reading other topics and built a smoke machine to try and find my leak. I did find a leak at the PTC gromett on the air flow hose before the turbo which I had replaced several weeks ago. I smoke tested the car again tonight and I couldn't see any leaks.

I am at a loss now where to go from here and I would appreciate any advice. Other work done that is related is PCV system replacement and throttle body clean. It got me stumped

Regards
Martin

[volvodoc]

You have to have a air leak causing this but a leak can also be a blockage of the oil trap or a broken hose trap to intake very common

[northernlights]

I think an air leak is a distinct possibility, somewhere downstream of the mass flow sensor. In the old days Bosch called it 'false air' when air entered the engine unmeasured.

If it is seemingly random then it may be worth looking for cracks at any non-flexible parts of the intake plumbing. Although it is tedious work, it may be worth removing and inspecting parts to see if there are cracks which may open under certain conditions when the engine moves a bit on its mounts.

Another possibility is a malfunctioning temperature sensor. The sensor doesn't have to be dead for this to happen, but instead reporting numbers out of specification. If the engine thinks the coolant (or air for that matter) is cooler/hotter than it actually is, then even though the O2 sensors will trim the A/F ratio to be correct, the mass flow numbers will appear to be wrong for a given load/torque demand from the engine.

For example, if the sensor is reporting high (coolant is colder than it should be) then the fuel trim will have to go rich (high) to satisfy the O2 sensors. For that matter, maybe the thermostat is misbehaving?

If you can locate a resistance vs temp chart for the sensor(s), I'd check them at two points:
1) Cold resistance after sitting overnight, and compare this to what it should be at ambient.
2) Hot resistance after the engine is fully warmed up, and compare it to what it should be at the stock thermostat open temperature, plus maybe 8C.

I say this because the stock rating on thermostats is when they start to open, and the full open rating is usually 15C higher, so split the difference for an estimate unless you have an better way of measuring the coolant temperature directly.

[jaces_dad]

i left my 03 2.5t with the key in position 2 and my battery died, when i jump started the car i had the same message and check engine light. I thought it was because my battery wasnt charged yet and the car drove just as it did before the battery died. if there a connection to this message and the battery dying? Sorry to bogart the thread

[VolvoEire]

Hi, I've a 2004 XC90 2.5L Diesel.

I get the "Engine Service Required" each and every time I pass 67 mph (i.e. only on a motorway).

The behavior is consistent and reproducible. I don't notice any performance problem at that speed though. Does this indicate an air leak or would it be more indicative of a temperature sensor problem.

Thks.