Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSBMW1993740IL (E32/2) V8-3982CC 4.0L DOHC (M60)REPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSDESCRIPTION AND OPERATIONENGINE CONTROL SYSTEM INPUTSSECONDARY IGNITION MONITOR
1993 BMW 740iL (E32/2) V8-3982cc 4.0L DOHC (M60)
Secondary Ignition Monitor
1993 BMW 740iL (E32/2) V8-3982cc 4.0L DOHC (M60)SECTION Secondary Ignition Monitor
Since M3.x, most Systems utilize a shunt resistor to additionally monitor the secondary ignition for misfire.
The resistor(s) is located in the wiring tray on the engine. It is connected in parallel to the ground lead (KL 4a) for the coils. As the secondary magnetic field collapses, a voltage spike is induced in the windings. The control module monitors the voltage drop across the resistor as an indication of coil firing. If a signal is missing, the control module detects the affected cylinder from the camshaft position sensor input.
The control module measures the duration of time it takes the monitored voltage drop for each ignition coil to dissipate below two volts. The time scale constantly changes based on engine speed.
- If there is no feedback signal present (0 volts) there is no spark present,
- If the 2 volt signal is not maintained long enough, the control module detects this as a week spark.
RENDER: 1.0x
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.