Some U5 category coils have a two-pin primary connector (example: U5001). In this case the diagnosis is the same as with classic single coils of the U1 category. See there for details.
Some coils of the U5 category are equipped with integrated ignition controllers (example: U5011). Therefore, in this case the primary resistance cannot be measured. On the “Signal1” (Trig) connector only the “switch” signal coming from the engine control module can be measured.
Measurement of secondary resistance
- To do this, it is necessary to identify the “Ground” pin in the connector, using a wiring diagram.
- Remove the coil, then measure resistance from the ground pin to the high voltage output of the coil.
Note: Some ignition coils contain diodes to suppress undesired sparks. If diodes are installed, resistance measuring is not possible.
This is the wiring diagram of a VW Sharan 2.8, engine code AYL. It uses coil type U5011.
The resistance of the primary coil cannot be measured due to the integrated ignition module. The resistance of the secondary circuit can be measured in between Pin2(GND) and the high voltage output.