U3870 Chevrolet Auto Trouble Code

U3870 Chevrolet OBD2 may also be triggered by faults earlier down the line. For example, a dirty MAF sensor might be causing the car to overcompensate in its fuel-trim adjustments. As a result, oxygen sensors are likely to report fuel mixture problems.

The computer notices the canister is empty when it detects a leaner condition (all the vapors are used up) and it resumes normal fuel delivery. Some car manufacturers then close the vent solenoid but leave the purge solenoid open. That creates a vacuum throughout the entire fuel storage system. Once the correct vacuum is reached, it closed the purge solenoid and waits to see if the vacuum holds.

U3870 Chevrolet Possible Solution:

Power Steering Pressure (PSP) Switch Malfunction In Key On, Engine Off Self-Test, this DTC indicates the PSP input to the PCM is high. In Key On, Engine Running Self-Test, this DTC indicates that the PSP input did not change state. Steering wheel must be turned during Key On, Engine Running Self-Test PSP switch/shorting bar damaged SIG RTN circuit open PSP circuit open or shorted to SIGRTN PCM damaged.

U3870 Chevrolet Description For All Models :

U3870 Chevrolet Trouble Repair :

If your vehicle failed a U3870 Chevrolet test and the U3870 Chevrolet Check Engine Light is NOT on, chances are you have a problem with the OBDII system, a burned out MIL lamp, or a faulty catalytic converter. The converter is essentially an afterburner that cleans up the exhaust after it exits the engine. The OBDII system uses a ownstream oxygen sensor to monitor the efficiency of the converter, and it should detect a drop in converter efficiency if the converter has been contaminated or is failing (ignition misfiring, leaky exhaust valves, and oil burning can all damage the converter). What you want to look any conditions that might cause ignition misfire, an overly rich or lean fuel condition, or loss of compression. Use your OBD Express DIY to look at the oxygen sensor outputs, coolant temperature, airflow, calculated engine load, and inlet air temperature.

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