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K. Wiggins
K. Wiggins, Chevy Technician
Category: Chevy
Satisfied Customers: 2514
Experience:  ASE Certified Technician AA in automotive Technology, 15+ years in the trade
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Looking wiring help 1995 Blazer, check engine light on. OBD1

Customer Question

Customer: Looking for ECM wiring help 1995 Blazer, check engine light on. OBD1 Code 15 - low Coolant Temp Sensor. Changed sensor. Changed Thermostat. Seems like electrical issue. traced wiring to ECM, cannot find any damage, all the way to the ECM. One wire is ground. Other wire comes from B9 in the red ecm connector. It is tan. All the pinout charts I can find say B9 is suppposed to be empty. Cannot find out why there is a tan wire from B9, and if it is supposed to be the wire connected to the CTS.
JA: Thanks. Can you give me any more details about your issue?
Customer: Also tried swapping out the ECM with a used one from a junk yard. No change, same error code.
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Submitted: 11 months ago.
Category: Chevy
Expert:  K. Wiggins replied 11 months ago.

Hello, B9 is for the intake air temperature sensor. I'll post the pin out chart and coolant sensor diagram below. Let me know how I can help further.

Customer: replied 11 months ago.
Thanks. Other pin out charts kept showing this as unused The air sensor is connected to another wire tho.
Customer: replied 11 months ago.
I'll check which in a bit No air sensor codes tho. Only code 15
Expert:  K. Wiggins replied 11 months ago.

You're welcome, here's the trouble chart for code 15. If you have a scan tool that shows live data it's a litle easier to troubleshoot. A volt meter works as well.

Customer: replied 11 months ago.
Thanks. So was able to switch the wire. B8 and B3 were already attached to the ECT sensor, even tho I was getting code 15. I attached the tan wire from B9 to the AIT as you recommended, but I had to disconnect another yellow wire that was already on the AIT (Not sure where this goes, its now attached to nothing. Its a separate yellow wire than the one on the ECT from B8.Anyway... the Code 15 seems to be gone for now, but now the engine runs for a 5 min or so idling then just stalls out. After sitting a while it will start again for 5 min or so then stall. No Error Code or Check Engine Light. However that one yellow wire I took from the AIT is not attached to anything.
Expert:  K. Wiggins replied 11 months ago.

Following that yellow wire from the intake air temp sensor back did it go to the computer?