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Smog Check Repair

2008 VW Jetta Air Monitor Not Getting Ready

I have checked that everything to set the monitor is correct, the ECT is at 77F, IAT 75F and ambient temp sensor is at 75F. When I start the car the vehicle doesn't activate the air pump. I checked the pump. It is good. The check valve is good as well. The relay and fuses are ok but the computer does not activate the air pump in the morning at all. There is no pending or hard trouble codes but the monitor doesn't get ready either.


We recommend diagnosing the air injection power system from the ECU on down to the actual pump itself. Somewhere along the system there must be a break. It's a bit tricky because the pump is only activated when the engine is cold so you only have a few minutes or so to test the ECU signal to the AIR relay. With an advanced OBD-II scan tool you may be able to trigger the AIR pump on manually.

That's the first step; finding out whether or not the ECU is in fact commanding the AIR relay on. If it is, diagnosing why power is not getting to the AIR injection pump should not be difficult. Make sure the relay is good, as far as the condition of it's contacts. Make sure the relay has resistance, as to indicate it is not burnt. Follow the power wire (+) from the relay to the pump. Is there power at the pump connector? How is gound (-)?

Back tracking a little bit... if there is no signal from the ECU to the air injection pump relay, and you've checked the wiring from the ECU to the the fuse/relay box (both power and ground), the diagnosis will require a bit more expertise. A smog repair technician will need to monitor the output of each sensor which is responsible for reporting engine temperature/condition data to the ECU; matching the variables with the ECU's expected values.

The mystery here is that the check engine light is not illuminated and that there aren't any trouble codes. This makes the diagnosis of this fault much more difficult.

posted by SmogTips Support 10-05-2017 01:13 PM

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