Well, problem solved for now. After the tech used a Multi Tester Pro scanner with Volvo software to turn on the air pump manually in the test mode, it's been working ever since. I installed an LED across the pump relay coil to see when the relay picks up and it comes on always after a cold start and...

Temperature guage is steady at 3 o'clock after warmup. This story continues to get stranger by the minute. A Volvo repair shop today scanned the ECM and was able to turn the pump on and off in the test mode. No diagnostic codes were present, no other indications of problems. What ever program logic ...

Thanks for the suggestion. I checked the wiring from the relay back to the ECM with a digital ohm meter and have a good circuit to the pin of the ECM socket.

I recently replaced the secondary air injection pump and injection valve after getting a secondary air injection code. The old pump was not working and the air injection valve was frozen closed. After about a week, the check engine light reappeared with the same code for secondary air. I've determin...