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 INPUTSLDP REED CONTACT FEEDBACK SIGNAL
1993 BMW 740iL (E32/2) V8-3982cc 4.0L DOHC (M60)
LDP Reed Contact Feedback Signal
1993 BMW 740iL (E32/2) V8-3982cc 4.0L DOHC (M60)SECTION LDP Reed Contact Feedback Signal
Introduced on the M5.2.1 and MS41.1 ORVR compliant engine control Systems, the LDP provides a means of testing the fuel/evaporative system for leaks. The pump is activated by ECM control. It pressurizes the fuel tank and evaporative system. The ECM receives a repetitive high/low voltage signal from the LDP as confirmation of LDP functionality and if the evaporative system is holding the pressure.
- The upper chamber contains an integrated reed switch that produces a switched high- low voltage signal that is monitored by the ECM. The switch is opened by the magnetic interruption of the metal rod connected to the diaphragm when in the diaphragm is in the top dead center position.
- The repetitive up/down stroke is confirmation to the ECM that the valve is functioning and the basis for determining if a leak is present in the system. The ECM monitors the length of time it takes for the reed switch to open, which is opposed by pressure under the diaphragm in the lower chamber. The LDP is still cycled, but at a frequency that depends upon the rate of pressure loss in the lower chamber.
RENDER: 1.0x
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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.