Troubleshooting Flowchart
Evaporative Emission (EVAP) Controls (cont’d)
(To page 11-155) (To page 11-155)
GRN
BLK/
YEL
VACUUM PUMP/GAUGE
A973X–041–XXXXX
EVAP
CONTROL
CANISTER
EVAP
PURGE CONTROL
DIAPHRAGM VALVEInspection of Evaporative
Emission Controls
Disconnect vacuum hose from
the EVAP purge control dia-
phragm valve (on the EVAP con-
trol canister) and connect a vac-
uum gauge to the hose.
Start the engine and allow it to
idle.
NOTE: Engine coolant tempera-
ture must be below 158°F
(70°C).
Is there vacuum ?
Disconnect the 6P connector
from the control box.
Measure voltage between BLK/
YEL (+) terminal and GRN ( – ) ter-
minal.
Is there battery voltage ?
Measure voltage between BLK/
YEL ( + ) terminal and body
ground.
Inspect vacuum hose
routing.
If OK. replace the
EVAP purge control
solenoid valve.
(From page 11-154)
(To page 11-156)
(From page 11-154)
Warm up the engine to normal
operating temperature (the cool-
ing fan comes on).
Check for vacuum at # 6 vacuum
hose after starting the engine.
Is there manifold vacuum?
Reconnect the hose.
Remove fuel fill cap.
Is there battery voltage ?
Inspect GRN wire for an open
between ECM (A20) and the
connector.
If wire is OK, substitute a
known-good ECM and recheck.
If symptom goes away, replace
the orignal ECM.
Disconnect the 6P connector
from the control box.
Is there manifold vacuum?
Inspect for a short to body
ground in GRN wire between
ECM (A20) and the 6P connec-
tor.
If wire is OK, substitute a
known-good ECM and recheck.
If symptom/indication goes
away, replace the original ECM.
Inspect vacuum hose
routing.
If OK, replace the
EVAP purge control
solenoid valve.
Repair open in BLK/
YEL wire between No.
2 fuse and the 6P con-
nector.
Emission Control System
Evaporative Emission (EVAP) Controls (cont’d)
(From page 11-155) VACUUM/PRESSURE GAUGE
0-4 in.Hg
07JAZ–001000A
PURGE AIR
HOSE
PURGE
HOSE
Connect a vacuum gauge to
purge air hose.
Start the engine and raise speed to
3,500 rpm.
Does vacuum appear on gauge
within 1 minute ?
See EVAP two way valve test to
complete.
Evaporative emission control are
OK.
Connect a vacuum gauge to the
canister purge hose and raise the
engine speed to 3,500 rpm.
Does vacuum appear on the
gauge?
Replace the EVAP control
canister.
Inspect the purge hose
and throttle body port
for pinch or blockage.