The most common causes of Alfa Romeo 164 U1679 code being stored are due to a defective intermediate shaft speed sensor, output speed sensor, or input speed sensor.
Common Symptoms For Alfa Romeo 164 U1679
One misplaced probe could destroy expensive control modules and require that the vehicle be totally reprogrammed. At the most, you may attempt to perform a continuity test after all control modules are disconnected, and this could literally require 40-hours or more, depending upon the vehicle
If the resistance level does not decrease with heat and increase as it cools, replace the sensor. If everything has checked out thus far, turn the key to the "ON" position and test for the presence of a voltage (and a ground signal) at the exhaust gas temperature/pressure (or heated oxygen) sensor electrical connector
Intermittent conditions can prove to be quite a challenge to diagnose and in extreme cases may have to be allowed to worsen before a correct diagnosis can be made. If the fuel shutoff valve has not been deactivated by a collision, use the digital volt/ohmmeter to test voltage and ground signals at the valve itself
If the fuel shutoff switch and all system circuitry checks out, suspect a defective PCM (or other related controller)
Auxiliary Emission Controls
Cruise Control Servo Indicates Low
TFP Valve Position Switch-Drive Without Drive Ratio
Alfa Romeo 164 U1679 Troubleshooting
If this is the case with the code, you will be hearing very loud noises, like explosions, from the rear of the vehicle upon acceleration. Firstly check the carburetor to ensure that the fuel and air combination are properly balanced. If these settings are correct, then thoroughly inspect the distributor cap for any cracks or hairline splits, as this can produce a backfire. Move on to the spark plugs and ensure that they are clean and undamaged and inspect the engine gaskets for any sign of damage, as they are responsible for ensuring the correct gas exchange within the engine. Alfa Romeo 164 U1679 OBD 2 code on vehicles with electronically controlled automatic transmissions, the 3-4 shift solenoid is responsible for actuating the hydraulic circuits to activate clutches or bands that change gears inside the automatic transmission.
How to turn off Alfa Romeo 164 U1679 check engine light ?
There are two ways to turn off the check engine light:
A repair technician can do so once repairs have been made.
The OBD II can automatically turn it off when it fails to detect the problem after several diagnostic cycles.