Troubleshooting Flowchart
Inspection of fuel pump relay.
Turn the ignition switch to START
(III) position.
Does the engine start?
Check for an open in the circuit:
1. Stop the engine.
2. Turn the ignition switch ON (II).
3. Measure voltage between
ECM connector terminal F4
and body ground.
Is there battery voltage?
Problem verification:
1. Start the engine. Hold the
engine at 3,000 rpm with no
load (A/T in position,
M/T in neutral) until the radia-
tor fan comes on, then let it
idle for at least one minute.
2. Turn the ignition switch OFF.
3. Disconnect # 4 hose from the
install pipe, connect vacuum
pump to the hose.
4. Apply vacuum 27 to 40 kpa
(200 to 300 mmHg, 8 to 12
in.Hg).
5. Start the engine.
6. Hold engine speed at 6,500
rpm (A/T in position,
M/T in neutral).
7. Measure voltage between
ECM connector terminal F4
and body ground.
Is there less than 1.0 V?
Inspect the fuel pump resistor
(see page 11-141).
ECM CONNECTOR F (26P)
WIRE SIDE OF FEMALE TERMINALS
(To page 11-140)
4 HOSE CONTROL
BOX
VACUUM PUMP/
GAUGE
A973X-041-XXXXX
Substitute a known-good ECM
and recheck. If prescribed volt-
age is now available, replace the
original ECM.
Fuel pump relay circuit is OK.
Fuel Supply System
Fuel Pump Relay
(From page 11-139)
FUEL PUMP RELAY 4P CONNECTOR
Check for open in the fuel pump
relay:
1. Turn the ignition switch OFF.
2. Disconnect the ECM connec-
tor F (26P) from the ECM.
3. Disconnect the 4P connector
from the fuel pump relay.
4. Connect fuel pump relay con-
nector terminals No. 2 to No. 4.
5. Turn the ignition switch ON (II).
6. Measure voltage between
ECM connector terminal F4
and body ground.
CAUTION: * the “A” connector must be
disconnected for this test or the ECM
will be damaged.
WIRE SIDE OF FEMALE TERMINALS
ECM CONNECTOR F (26P)
WIRE SIDE OF FEMALE TERMINALS
Is there battery voltage? Replace the fuel pump relay.
Check for an open in the wire:
1. Remove the jumper wire.
2. Measure voltage between the
fuel pump relay connector ter-
minal No. 2 and body ground.
Is there battery voltage?
Repair open in wire between the
fuel pump relay and the No. 5
BACK-UP LIGHTS ALTERNATOR
TURN SIGNALS (15 A) fuse in the
under-dash fuse box).
Repair open or short in wire
between ECM (F4) and the fuel
pump relay.