Models Produced From March 1990
RELAY OPERATIONAL CHECK1. With ignition OFF, remove fuse #13.
2. Check for voltage between terminals of fuse holder and ground.
^ Both terminals should have zero volts.
3. Turn ignition ON and check for voltage again as in step 2.
^ One terminal of the fuse holder should have battery voltage for 1-5 seconds after ignition is turned ON.
4. Connect voltmeter between the fuse terminal that showed voltage and ground.
5. Briefly operate starter and note voltage.
^ Should have battery voltage while cranking.
5. Remove fuse #28 and repeat steps 2-5 for #28 fuse holder. All test results should be the same as for fuse #13.
If voltage is present at both fuse holder #13 & #28 during cranking and when ignition is first turned ON, then relay and control signal are OK. Further testing is not necessary.
If voltage is not present in step 3 or 5, or if voltage is present in step 2, for either fuse holder, remove fuel pump relay and perform the following checks in the order shown.
Fuel Pump Relay Socket Terminal ID:
VOLTAGE SUPPLY CHECK
1. With ignition turned OFF, check for voltage between socket terminal 48 and ground (hot from battery all the time).
^ Should have battery voltage.
If not, check for open circuit between fuel pump relay socket terminal 48 and battery positive terminal. Repair as necessary.
2. Turn ignition ON and check for voltage at socket terminal 46 (hot from ignition switch).
^ Should have battery voltage only when ignition is ON.
If there is no voltage, check for open circuit between fuel pump relay socket terminal 46 and ignition switch terminal 15.
If there is voltage when ignition is OFF, check circuit between socket terminal 46 and ignition switch terminal 15 for short to power. Also check for ignition switch terminal 15 shorted internally to power at switch terminal 30. Repair wiring or replace switch as necessary.
If relay failed operational check and passed voltage supply check, then proceed to continuity check.
CONTINUITY CHECK
1. Check for continuity between:
a. Relay socket terminal 50 and ground.
b. Relay socket terminal 47 and ECU terminal 15D.
c. Relay socket terminal 52 and fuse #13.
d. Relay socket terminal 59 and fuse #28.
^ Should have continuity with not more than 0.5-0.8 ohms resistance.
If there is no continuity in any one of the four circuits, repair open in wiring for that circuit, and re-check fuel pump relay operation.
If there is continuity in all four circuits, proceed to signal check.
SIGNAL CHECK
The fuel pump relay is energized when relay terminal 47 is grounded through ECU terminal 15D.
1. With fuel pump relay removed and ignition turned OFF, connect voltmeter between socket terminals 46 (power from ignition switch) and 47 (ground side of relay) and note voltage.
^ With ignition OFF voltage should be zero or near zero.
If voltage is present, check for short to ground in circuit between fuel pump relay socket terminal 47 and ECU terminal 15D. Repair as necessary.
If voltage is present and no wiring problems are found, then ECU is faulty (ECU terminal 15D shorted to ground internally-fuel pump relay energized with ignition OFF).
2. Turn ignition ON and note voltage.
^ With ignition ON, voltage should be battery voltage for approx. 1-5 seconds.
If not, ECU is faulty (no ground signal for fuel pump relay when ignition turned ON).
3. Briefly operate starter and note voltage.
^ Battery voltage should be present when cranking.
If not, ECU is faulty (no ground signal for fuel pump relay when cranking).
If relay failed the operational check but the continuity check, voltage supply check and signal check are OK, then the fuel pump relay is faulty (replace relay).