LAST EDITED ON Dec-29-02 AT 03:46 PM (EDT)
Goldbadge - The DPFE sensor is NOT part of the EGR valve - Here's what I found using the service manual CD:-----------------------------------------------------------------
Remember:
To prevent the replacement of good components, be aware that the following non-EEC areas may be at fault:
l Damaged EGR valve
l Restricted exhaust
l Damaged vacuum reservoir
This Pinpoint Test is intended to diagnose only the following:
l Harness circuits: VREF, DPFE, SIG RTN, EVR, VPWR
l PFE sensor (9D460)
l EVR solenoid (9J459)
l Powertrain Control Module (PCM) (12A650)
l DPFE sensor (9J460)
l EGR valve assembly
l Vacuum lines (EVR, PFE/DPFE)
l DPFE Sensor Pressure Hoses
Description
The Pressure Feedback Electronic (PFE) EGR system consists of a pressure sensor (PFE sensor), Electronic Vacuum Regulator (EVR) solenoid, and a vacuum actuated EGR valve. The Differential Pressure Feedback Electronic (DPFE) EGR system uses a differential pressure sensor (DPFE sensor) that has two pressure inlets. The PFE system has one pressure inlet in the sensor.
In both systems, the EVR solenoid regulates a vacuum signal to the EGR valve in response to a duty cycle signal from the Powertrain Control Module (PCM). The EVR solenoid will vent some of the source vacuum and transmit the remaining vacuum to the EGR valve in response to the level of the duty cycle. The higher the duty cycle, the more vacuum transmitted to the EGR valve. Due to the design of the EVR solenoid, the vacuum at the EGR valve never reaches the source vacuum level.
EGR flow rate is determined by monitoring the pressure across a fixed metering orifice as exhaust gasses pass through it. The DPFE system monitors this flow across the orifice by supplying the DPFE sensor with a pressure signal before the orifice (upstream pressure) and a pressure signal after the orifice (downstream pressure). The DPFE sensor then evaluates these two pressure inputs and determines the pressure difference across the orifice. This pressure difference translates to a specific EGR flow which the DPFE sensor signals the PCM by an analog voltage signal. This signal to the PCM increases linearly as the differential pressure increases. The PFE system, unlike the DPFE system, has only one pressure signal input (downstream) and must rely on the PCM to indirectly infer the upstream exhaust pressure in order to determine the EGR flow rate. The PFE sensor transmits an analog voltage signal which decreases linearly as EGR flow increases.
The PCM optimizes the EGR flow rate by varying the EVR duty cycle using the feedback signal the PFE or DPFE sensors provide.
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Here is diagnostic info for your 326 code...
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DTC 326 or 327 indicates the DPFE circuit voltage is lower than expected at zero duty cycle.
l Key off.
l Check PFE/DPFE sensor pressure input hose(s) for obstruction and/or leaks.
l Are there any obstructions or leaks?
Yes
SERVICE as necessary. RECONNECT all lines. RERUN «Quick Test».
No
GO to «DL23»...
DL23 CHECK PFE/DPFE SIGNAL VOLTAGE WITH ENGINE AT IDLE
l Key off.
l Disconnect Powertrain Control Module (PCM). Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary.
l Install breakout box and connect PCM to breakout box.
l Start engine and idle with transmission in PARK or NEUTRAL.
l Measure voltage between Test Pin 27 and Test Pin 46 at the breakout box.
l Is voltage less than 2.9 volts (PFE) or 0.2 volt (DPFE)?
Yes
For DPFE Applications:
REPLACE DPFE sensor. REMOVE breakout box. RECONNECT all components. RERUN «Quick Test».
For PFE Applications:
GO to «DL24».
No
REPLACE PCM. REMOVE breakout box. RECONNECT all components. RERUN «Quick Test».
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Diagram of DPFE system
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Hope this helps!
-Scott
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