Secondary Air Valve, pump or O2?

AxisF80 · 03-21-2019, 09:31 PM

Got a check engine light tonight and used my BT Tool to pull codes.

It shows codes 27E1 and 27B0

I've heard an intermittent whirring sound lately. Any advice if I should start with the Secondary Air Pump, valve or 02 sensor would be greatly appreciated.

Car is an 09 M3 with 71k miles.

deansbimmer · 03-22-2019, 08:30 AM

You'd need to run individual tests for the Secondary air system and for the lambda control. Not sure if Bavarian software can do that, but ISTA can.

The DME monitors secondary air flow into the exhaust via the system's MAF sensor, and differentiates bank 1&2 air injection by lambda control monitoring oxygen in each exhaust stream. If the o2 sensor doesn't see the target oxygen volume in that bank then it will throw a fault. So, if the oxygen sensor is faulty it may cause an erroneous fault- so that's why further tests would be needed (unless you want to throw parts at it).

You would have different codes if the pump itself was inop, but most scantools have a SAP test mode as well. The pump is probably OK.

If the exhaust at cold start smells particularly gaseous, it may be another clue that the valve is stuck closed.

03-21-2019, 09:31 PM	#1
AxisF80 Private 29 Rep 79 Posts Drives: 2009 E90 M3 Join Date: Dec 2009 Location: NJ iTrader: (1)	Secondary Air Valve, pump or O2? Got a check engine light tonight and used my BT Tool to pull codes. It shows codes 27E1 and 27B0 I've heard an intermittent whirring sound lately. Any advice if I should start with the Secondary Air Pump, valve or 02 sensor would be greatly appreciated. Car is an 09 M3 with 71k miles. Attached Images Last edited by AxisF80; 03-21-2019 at 09:40 PM..
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03-22-2019, 08:30 AM	#2
deansbimmer BimmerPost Supporting Vendor 4324 Rep 3,023 Posts Drives: 2011 E93 M3 Join Date: Nov 2014 Location: DFW, Texas iTrader: (17) Garage List 1988 E30 M3 [0.00] 2006 E46 M3 [0.00] 2024 X7 M60i [0.00] 2011 BMW M3 [0.00]	You'd need to run individual tests for the Secondary air system and for the lambda control. Not sure if Bavarian software can do that, but ISTA can. The DME monitors secondary air flow into the exhaust via the system's MAF sensor, and differentiates bank 1&2 air injection by lambda control monitoring oxygen in each exhaust stream. If the o2 sensor doesn't see the target oxygen volume in that bank then it will throw a fault. So, if the oxygen sensor is faulty it may cause an erroneous fault- so that's why further tests would be needed (unless you want to throw parts at it). You would have different codes if the pump itself was inop, but most scantools have a SAP test mode as well. The pump is probably OK. If the exhaust at cold start smells particularly gaseous, it may be another clue that the valve is stuck closed.
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