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Hello, I just did a motor swap in a 1988 chevy k2500 with the 5.7 liter engine. The motor swapped in is from a 1995 k3500 and is also a 5.7 liter. While looking at the data feed from tuner pro i noticed that the truck does not go into closed loop. There are no check engine lights on. What would cause the ecm not to run in closed loop?
Did the swap include the ECM?
Bob
No. Everything stayed just the motor was swapped.
There are a couple of possibilities, if it used to run closed loop. First make sure that you are seeing the o2 sensor swing, If it doesn't see an o2, it wont go closed loop. Second, look at the coolant temp, it wont go closed loop until it warms up. also you could be in limp mode.