I have 97 trek and the DTC code is 4011 I have replaced the front O2 sensor, the secondary air pump and the egr and it still reads that I have secondary air injection problems (Incorrect flow) can anyone help, and does anyone have a vacuum line schematic for a trek
Make sure the air pump works. The air pump takes air from the intake and puts it into the exhaust, to "reduce" emissions. Check the fuses/relays, electrical connections, and air tubing. A vacuum diagram won't help you. Unplug the pump, and use two jumper wires from the battery to give the pump power and a ground to see if it works. Also, get a test light and connect it to the + and - terminals in the air pump connector on the harness, and have someone turn the key on, without starting the motor. The test light should light up for a moment. If not, there is a problem with the power (ie fuse, relay, or signal from ECM) or ground. You can also use the test light to check each side of the circuit.
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