EGR System - MIL is ON Intermittently
90saab06 CATEGORY EngineSECTION PAGE
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ISSUE CODE
10/90-0027 254
Subject: Illumination of "Check Engine" Lamp
Application: 1990 900 and 9000 Models with Electronic EGR
Some 1990 models equipped with the electronic EGR system may experience intermittent illumination of the "Check Engine" lamp even though there are no engine or emission control-related faults. To remedy such cases, a wiring harness for the EGR system is available as a service solution.
Before installing the harness, read all stored fault codes in the LH System. The fault codes for the EGR system are 46391/26391 (ISAT) and 12245 (Blinking Light Code). A check of the components in the EGR system should also be carried out.
Figure 1:
EGR System Component Checks
1. Using ISAT, enter command code 555 and check that the modulating valve is working. If the valve is NOT working, proceed to step 2. If the valve is working properly, proceed to step 4.
2. Check for continuity between pin 19 on the LH ECU and Pin 2 on the modulating valve (Figure 1).
3. Check for voltage at Pin 1 of the modulating valve with the ignition key in the "On" position (Figure 1).
Figure 2:
4. Check for continuity of the yellow/white wire between the EGR NTC and Pin 23 on the LH ECU (Figure 2).
5. Make sure there is a good ground at the black wire on the NTC (Figure 2).
Figure 3:
6. Inspect all of the vacuum hoses for the EGR system to ensure that none of them are disconnected, misrouted or damaged in any way (Figure 3).
7. Using a hand-held vacuum pump, check the following components:
^ EGR Valve: Make sure that the valve holds a steady vacuum without any drop in the reading.
^ Check Valve: See that the valve is open in one direction and closed in the opposite direction.
^ Vacuum Tank: With one of the nipples plugged, ensure that the tank will hold a steady vacuum without any drop in the reading.
Figure 4:
8. Overflow valve (Turbos only): Make sure that the passage through the top of the tee is open in both directions (Figure 4).
^ Apply pressure from a hand held source to one side of the tee while blocking off the opposite side. This should result in the opening of the bottom port at approximately 0.4 to 0.5 bar.
^ The valve should not leak from the top area.
Figure 5:
Service Wiring Harness Installation
After completing all of the component checks and correcting any faults found, install the service wiring harness, P/N 02 45 258 in between the two halves of the 2-pole connector for the EGR system NTC sensor (Figure 4).
Clear all fault codes from the system and road test the car to verify the repair.
Warranty Information:
For warranty claims, use Failure Coding 25439-67-0-01-05. Time allowance is 0.5 hours straight time (0.4 for diagnostic steps and 0.1 to install service wiring harness.)