DL - Testing Notes

NOTE: You should enter this Pinpoint Test only when you have been directed here from Quick Test.

REMEMBER

To prevent the replacement of good components, be aware that the following non-EEC areas may be at fault.


- Damaged EGR valve

- Restricted exhaust system

- Damaged vacuum reservoir or canister


This Pinpoint Test is intended to diagnose only the following:

- Harness circuits: VREF, PFE, DPFE, SIG RTN, EVR, VPWR

- PFE sensor

- DPFE sensor

- EVR solenoid

- EGR valve assembly

- Processor assembly

- Vacuum line/tubes (EVR, PFE/DPFE)


DESCRIPTION


The DPFE and PFE sensor are solid-state pressure transducers. The sensors convert EGR pressure into an analog voltage signal. The processor uses a digital equivalent of the analog voltage signal to control EGR flow, ignition timing and air/fuel ratio. The PFE sensor monitors pressure on one side of a metered orifice, while the DPFE sensor monitors the pressure on both sides of a metering orifice and calculates the presure differential.

The processor controls the amount of vacuum applied to the EGR valve by sending a control signal to the EVR solenoid. As the duty cycle of the processor control signal increases, vacuum to the EGR valve diaphragm increases, yielding an increase in EGR flow.