EGR Function Testing - Diesel Isuzu Isuzu Trooper I

I-Mark, Pickup & 1987 Trooper II With Diesel Engine

Disconnect hose from EGR valve. Apply 18 in. Hg to EGR valve and ensure EGR valve opens fully. Reconnect hose to EGR valve. Warm engine to operating temperature. Increase engine speed to 2500-3000 RPM. EGR valve should open. If system operates as indicated, system is functioning properly.

Scheme 5

NPR 3500 5.2L Diesel

The engine control module (ECM) controls the EGR valve opening based on the atmospheric pressure, engine speed, engine coolant temperature, intake air temperature and fuel injection quantity. The ECM controls the EGR valve by controlling the EGR DC motor. The EGR valve position is detected by the EGR position sensor, and relayed to EGM via the EGR position sensor.

Conditions for running the EGR control

1. The battery voltage is more than 11 volts.
2. The barometric pressure is more than 11.6 psi (80 kPa).
3. The engine speed is higher than 570 RPM.
4. The engine coolant temperature is between 149°F (65°C) and 198°F (92°C).
5. The intake air temperature is between -40°F (-40°C) and 185°F (85°C).

Conditions for canceling the EGR control

1. The barometric pressure went less then 11.3 psi (78 kPa).
2. The engine speed dropped below 570 RPM.
3. The engine coolant temperature exceeded 203°F (95°C), or dropped below 144°F (62°C).
4. The intake air temperature exceeded 185°F (85°C), or dropped below -49°F (-45°C).
5. Certain DTCs have been set.

EGR System Test

1. Install scan tool. Turn off the ignition for 30 seconds. Turn on the ignition, with the engine off Monitor the Diagnostic Trouble Code (DTC) information of the engine control system with a scan tool and check whether any of the following DTC(s) are set: P0087, P0088, P0089, P0091, P0092, P0102, P0103, P0117, P0118, P0182, P0183, P0192, P0193, P0201-P0204, P0237, P0238, P0239, P0299, P0335, P0400, P0405, P406, P0606, P642, P0643, P1093, P1094, P1261, P1263, P1264, P1265, P1266, P1404, P2152, P2155, P2228, P2229 orP2293. Are any of these DTCs set? If yes, see appropriate diagnostic information. If no, go to next step.
2. Inspect the EGR components for the following conditions: EGR gas leakage any of the EGR passage between the exhaust manifold and the intake manifold. Check for damaged components and for loose fixing. Restricted or collapsed EGR passage between the exhaust manifold and the EGR valve. Did you find and correct the condition? If yes, go to Step 7. If no, go to next Step.
3. Start the engine and let it idle. Warm up the engine (engine coolant temperature is between 149°F (85°C) and 198°F (92°C). Observe the Desired EGR Position and EGR Position Sensor parameter with a scan tool. Is the difference between the Desired EGR Position and EGR Position Sensor less than 5%? If yes, system is OK. If no, go to next Step.
4. Perform the EGR Control with a scan tool. Command the Position Increase and Decrease with a scan tool. Observe the EGR Position Sensor parameter with a scan tool. Does the EGR Position Sensor parameter follow the Desired EGR Position parameter? If yes, go to Step 6. If no, go to next Step.
5. Remove the EGR valve. Inspect the EGR valve for restricted valve. Repair the condition as necessary. Did you find and correct the condition? If yes, go to Step 7. If no, go to next Step.
6. Replace the EGR valve. Did you complete the replacement? If yes, go to next Step.
7. Install a scan tool. Start the engine and let idle. Warm up the engine (engine coolant temperature is more than 149°F (65°C). Observe the Desired EGR Position and EGR Position Sensor parameter with a scan tool. Is the difference between the Desired EGR Position and EGR Position Sensor less than 5%? If yes, system is OK. If no, go to Step 2.