Check Engine Light after New MAF Sensor

wahoouva2 · Post by **wahoouva2** » 11 Jan 2013, 08:30

I have a 2005 XC90 2.5 that started idling rough and OBD gave me P0101 code. Cleaned the MAF sensor and unhooked battery to reset the computer, Check Engine light came back on after a short drive. Still got P0101 code, so I bought a new MAF and put it on it last night and unhooked battery. After a short drive, same result, check engine light came on. It doesn't seem to be idling rough or impaired the acceleration or performance.

Any thoughts on what could be causing this Check Engine light? And if it starts idling rough again, I know it isn't the MAF sensor, what else could it be?

The O2 Sensors checked out okay on the OBDII.

Thanks

Post by **boosted5cyl** » 11 Jan 2013, 09:14

could be a cabling issue. Not sure if it applies to the XC, but the T5 in the 850 and early V70's required a zippy tie to be applied to it to stop the cable wiggling around and causing similar issues.

You could log g/s on the OBD reader and see if there are dropouts or other anomolies.

Post by **precopster** » 11 Jan 2013, 10:48

Test between input pins 2 & 4 for around 1.6 volts at idle. While doing this jiggle the cable to see if the reading fluctuates or drops out.

cbotd · Post by **cbotd** » 22 Jan 2013, 11:35

I have a similar issue. 2005 XC90 T5 with 96k miles.

CEL came on yesterday and P0101 was the error code. I cleaned the MAF sensor, replaced the air filter and have not reset the computer yet. CEL is still on. I did notice a sucking noise while the hood was up and the engine was running. I tracked info down on MVS here and it may be a PCV or air leak causing the CEL to illuminate.

It's 19 degrees and snowing so I may not tackle the issue today, but you may want to listen for an air leak yourself. Also, for rough idle you might want to consider cleaning the throttle.

cbotd · Post by **cbotd** » 24 Jan 2013, 15:29

Update: Replaced the MAF sensor. CEL was reset and came back on within 50 miles.

This time I have a very loud sucking noise coming from the airbox and the car will stutter and then backfire. However, this does not happen every time I accelerate or give the car gas. I have inspected all of the hoses I can fell and see from the airbox to the turbo. All lines seem to be in good shape.

I'm beginning to wonder if the Waste Gate Actuator might be acting up. Sporadic sluggish acceleration (feels like no boost) with a loud sucking noise and a popping backfire from the exhaust. Idle is fine at this point and I can feel the turbo kick in when the sucking noise and backfire are not happening.

Thoughts or ideas?

Post by **boosted5cyl** » 25 Jan 2013, 15:13

Sounds like a vacuum leak to be honest.

cbotd · Post by **cbotd** » 30 Jan 2013, 11:37

Diagnosis complete. I have a faulty Fuel Pressure Sensor. Part and labor from my specialist is $300 to replace.

cbotd · Post by **cbotd** » 05 Feb 2013, 07:28

Following up on this thread due to the generic nature of the P0101 ODB II code. Hopefully this will help someone out in the future.

First Code P0101 - No drive ability problems or noticeable issues. Cleaned the MAF and replaced the air filter. Cleared CEL manually.

Second Code P0101 and P2178 - Codes appeared 47 miles after CEL reset. I now had a noticeable shudder under load, a rich fuel smell and a backfire. Gas mileage was also affected negatively.
- Diagnosed as a ad Fuel Pressure Sensor. Parts and labor $296. Cleared CEL manually.
- Inspected vacuum lines for leaks at this time as well. No leaks detected.

Third Code P0101 - Code appeared 47 miles after reset. No noticeable drive ability problems. Gas mileage a little less than average. Recommended from mechanic that I replace the MAF w/ Bosch / Volvo equipment.
- Replaced MAF sensor. Cleared CEL Manually.

Fourth Code P0101 - Code appeared 47 miles after reset. Took to Volvo dealer for further diagnosis.
- Volvo tech diagnosed the throttle body as needing cleaning. $337 from dealer.
- Dealer also flashed and updated the car's software. $99 value, no charge to me

- Tested for PCV issues and all pressure tests indicated no problems with crank case, system is not clogged

I only have 12 miles on the XC90 after the dealer service, but have been told the issue was resolved. P0101 is very generic. Dealer have the tools to help pinpoint the issue and set a corrective action plan without chasing a series of costly options as I did.