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Ron, ASE Certified Technician
Category: Chevy
Satisfied Customers: 35503
Experience:  35 years experience with ASE Certs
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I have a 2007 Chevrolet Trailblazer 4.2l... I have a 2007

Customer Question

I have a 2007 Chevrolet Trailblazer 4.2l... I have a 2007 Chevrolet Trailblazer 4.2l the secondary air pump won't come on. I replaced the air pump , air solenoid, relay to the pump and relay to the air solenoid. I jumped the connecters at the pump relay,
and the pump came on. Everything has power at the pump relay but the PCM is not commanding the relay to ground through the brown wire. I replaced the PCM and the pump still didn't come on. I didn't want to pay for a crankshaft relearn so I returned the PCM
and put the old PCM back in. The temperature sending unit is reading the right temperature with my code reader. The O2 sensors are oscillating twice a second 1 volt. When I ground the brown wire to the relay the air pump works. I have good continuity to the
PCM with the brown wire. Any help would be appreciated.
Submitted: 1 year ago.
Category: Chevy
Customer: replied 1 year ago.
Since a different PCM didn't work something else must be telling the PCM not to ground the brown wire.
Expert:  Ron replied 1 year ago.

Hello, my name is ***** ***** I am a professional here at Just Answer. I have noticed that your question was not getting a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.

With the pump not running the computer should be detecting and setting a fault code, can you get me the fault code and or codes and post back with them and I will try and help you get this resolved.

Customer: replied 1 year ago.
No codes yet I only drove it 30 miles.
Expert:  Ron replied 1 year ago.

Are you sure the pump is not cycling as it should. If its not there should be a fault code. Drive it some more when you can and lets see if a code sets. Let me know and we can work from there.

Customer: replied 1 year ago.
After you told me to ground the brown wire and see if it runs and it ran. I checked for continuity to the PCM which was good. I then cleaned the connecter at the PCM and the relay with the brown wire. The connector at the relay with the brown wire looked corroded somewhat with something white I tried to scrape it off as much as possible and used Electrical spray. The pump has ran the last two times which is a first. Code 411 came up when I had the hose disconnected at the solenoid to feel it running. I reset the codes and nothing came up today. Thanks for bringing my attention to the brown wire hopefully all is good.
Expert:  Ron replied 1 year ago.

It dose sound like you may have gotten it resolved. If there is still a problem the computer will set and store a fault code at some point. If no codes come up then you should be good to go.

Customer: replied 1 year ago.
This morning the check engine light came on again. I checked the codes 411 didn't come up. But PO420 Catalyst Below threshold bank 1. P1400 PCM not in spec on cold starts. PO 171 system too lean bank 1. Since the secondary air pump is now running would disconnecting the negative battery for 30 minutes reset the computer and have the computer start fresh be any help. The catalytic converter is 6 months old.
Expert:  Ron replied 1 year ago.

Yes disconnecting the negative battery cable will reset the computer. Let try that and see if anything returns.

Customer: replied 1 year ago.
Ok sounds good
Expert:  Ron replied 1 year ago.

Post back if you end up with some new codes and we ca work from there. Please take a moment to rate my service so I can get credit for my time, the question remains open for follow up even after doing so, all you need to do is return to this question if need be.

Thank you again.

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