Car is a 2004 coupe with auto trans and approx 35,000 miles. Yesterday after an approximate 20-mile run on the freeway, I noticed that the aux air pump was running after I shut the engine down and removed the ignition key. I waited five minutes to see if the pump would shut down - it didn't. I then removed the wire connector on the pump and it (of course) stopped. I quickly connected it again and pump started running (always engine off and key removed). I removed the connector again and waited around 30 minutes. I plugged in the connector and this time the pump didn't run, which to my knowledge is normal. Is there anything strange going on here? I know that the aux pump is supposed to run around 90 seconds after a cold start (to speed-up cat warm-up), but run again after engine shut-down? Comments appreciated.

 

I am not sure if there is power to the RCM with the ignition OFF, if there is then the relay points might have stuck for a while. Fix it quick or a new pump will be required as the pump might run all the time if they are stuck together. It will not cure itself, it will just get worse.

 

All relays in the RCM Except the traction control relay are powered directly off splice block 100, it is fed by the 200 amp fuse in the box next to the battery. Hot all the time.

You have a sticky relay. Change the RCM itself or yank it and send it to Tighd1 in Arizona and for around $35 it will come back all fixed and pretty.

 

As I reported in my original post, last week my aux air pump kept running after I shut the engine off. I was about 20 miles from home, so I quickly drove home, shut down, and saw that the aux pump was still running. Waited 10 minutes and it finally stopped. Thinking it was a bad relay in the relay module, I replaced the module with a known good spare I had on hand, but the aux pump didn't run when I started the engine cold the next morning. A check with test leads revealed that the pump is kaput. Incredible price range for these pumps - from a $100+ Brand X on eBay to $300+ at an MB dealer to $1,000+ at a Chrysler dealer. Found a Bosch air pump online for less than $200. Looks like the way to go. A question remains. If the relay was OK, how can you explain the aux motor running after engine shutdown? All I can think of is that the relay stuck temporarily to the point where the aux motor burned out.

 

The pump can be rebuilt sometimes if you are clever with your hands.
There is a thread on it in the "Index of Crossfire ......" .

 

Thanks for the response and the advice. I'll take the air pump apart and see what's what.
Couldn't find the thread you mentioned.

 

Sorry, it fell of the list somehow. CLICK

 

pump can not run without power, so you had a stuck relay or bridged wire thats pinched. A stuck relay is like a unexploded bomb. Touching the case is enough of a shock to open up contacts that were wedged or partially welded. Woody