Hyundai Sonata LF: Engine Control System / Injector Troubleshooting
The three waveforms below are taken from the #1 and #4
injectors. The top waveform is from the high side (feed side) of the #1
and #4 injectors, while the middle waveform is from the low side (ground
side) of the #1 injector and the bottom waveform is from the low side
of the #4 injector.
The middle waveform is the same as the top waveform because
there is no ground for the circuit. With no current flowing in the
circuit, the #1 injector is not energized and fuel does not flow.
The bottom waveform shows that ground is supplied and there
is a voltage drop across the #4 injector. With current flowing in the
circuit, the #4 injector is energized and fuel flows.

Other information:
Inspection
1.
Turn the ignition switch OFF.
2.
Disconnect the HO2S connector.
3.
Measure resistance between the HO2S terminals 2 and 5 [B1/S1].
4.
Measure resistance between the HO2S terminals 3 and 4 [B1/S2].
5.
Check that the resistance is within the specification...
Replacement
When prying with a flat-tip screwdriver or use a prying trim
tool, wrap it with protective tape, and apply protective tape around the
related parts, to prevent damage.
1.
Disconnect the negative (-) battery terminal...