Isuzu 1999 RODEO Workshop Manual page 869

6E1–242 RODEO X22SE 2.2L ENGINE DRIVEABILITY AND EMISSION
Diagnostic Aids
Due to the moisture associated with exhaust systems, the
EGR valve may freeze and stick in colder weather at
times. After the vehicle is brought into a warm shop for
repairs, the valve warms and the problem disappears. By
watching the Actual EGR and Desired EGR Positions on
a cold vehicle with a Tech 2, the fault can be verified
easily. Check the freeze frame data to determine if the
Diagnostic Trouble Code set when the vehicle was cold
by viewing the Engine Coolant Temperature (EGR).
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart:
1. The Powertrain OBD System Check prompts the
technician to complete some basic checks and store
the freeze frame and failure records data on the
Tech 2 if applicable. This creates an electronic copy
of the data taken when the fault occurred. The
information is then stored on the Tech 2 for later
reference.
2. Commanding the EGR valve open determines
whether the EGR system can control the EGR valve
accurately and if the fault is present.
3. If the EGR valve 5 volt reference is shorted to
ground, the DVM will read no voltage and an
additional Diagnostic Trouble Code will be set and
engine performance will be poor. When this circuit
is open, only a Diagnostic Trouble Code P0405 will
be set.
Step
1 Was the Powertrain On–Board Diagnostic (OBD)
System Check performed?
2 1. Turn the ignition switch ON, with the engine OFF.
2. Install a Tech 2.
3. Command the EGR valve to the specified values.
Does the Actual EGR Position follow the Desired EGR
Position?
3 1. Turn the ignition switch ON, with the engine OFF.
2. Disconnect the EGR valve electrical connector.
3. With a Digital Voltmeter (DVM) connected to
ground, probe the 5 V reference circuit to the EGR
valve.
Does the DVM read near the specified value?
4 Jumper the EGR valve 5 volt reference circuit to the
signal circuit.
Does the Actual EGR Position display the specified
value?
5 1. Connect the test light to B+.
2. Probe the 5 V reference circuit to the EGR valve.
Does the test light illuminate?
DTC P0405 – EGR Sensor Circuit Low
Action
4. Jumping the 5 volt reference circuit to the signal
circuit checks the signal circuit and PCM. The Tech
2 should display the Actual EGR Position as 100% if
the signal circuit and PCM are OK.
6. Although the PCM and circuitry acted correctly in the
previous step, a problem may still lie within the
terminals which would not show up in probe type
testing. Check the terminals for being backed out,
improperly formed or damaged, and for poor
tension.
10. All circuits to the EGR valve are OK at this point.
The fault lies internally in the EGR valve and
therefore must be replaced. Be sure all gasket
material is removed from the EGR mounting
surface. Even a small amount of material may
cause a Diagnostic Trouble Code P0405 to set.
Refer the EGR Valve for on vehicle service of the
EGR valve.
13. The replacement PCM must be reprogrammed and
the crankshaft position system variation procedure
must be performed. Refer to the latest procedures
for PCM reprogramming and Powertrain Control
Module for the Tooth Error Correction Variation
Procedure.
14. Check the terminals for being backed out,
improperly formed or damaged, and for poor
tension.
Value(s)
— Go to Step 2
25%, 50%,
Go to Step
75%, 100%
5 V Go to Step 4
100% Go to Step 6
— Go to Step 8
Yes No
Go to
Powertrain
OBD System
Check
15 Go to Step 3
Go to Step 5
Go to Step 7
Go to Step 9