Hard Or Intermittent Trouble Code E20: Notes

When ignition is turned on, ECM energizes fuel pump relay for 2 seconds which feeds 12 volts to fuel pump circuit (No. 120). As soon as distributor reference pulses are received, ECM energizes relay so that fuel pump circuit is fed 12 volts while engine is running.

Trouble code indicates that fuel pump relay circuit did not supply 12 volts to fuel pump. Possible causes are: Faulty fuel pump relay, defective wiring, terminals, etc., ECM not processing fuel pump feedback voltage properly or not switching fuel pump relay on, or shorted fuel pump.

1. To determine if code is hard or intermittent, turn ignition off for 10 seconds to "power down" ECM. Turn ignition on for 5 seconds and then attempt to start engine. If engine now starts but code is not stored hard, then malfunction is not present at this time. If engine will not start, check fuel pump fuse. If engine starts with hard code stored, it must then be determined if ECM is receiving proper feedback signal. If engine data parameter P.1.0 reads 0 volts, then check circuit No. 120 leading to ECM for an open. If circuit is okay, check for faulty ECM connector or faulty ECM.
2. If engine will not run and fuel pump is okay, or if engine starts and parameter P.1.0 reads battery voltage, next step is to verify if ECM is supplying a signal to fuel pump relay. This can be done by removing fuel pump relay and probing cavity No. 5 with test light to ground. If test light on circuit No. 465 does not light, reinstall fuel pump relay and then check circuit for an open or short to ground. If circuit No. 465 is okay, check for faulty ECM connector or faulty ECM. If short to ground is discovered, it must be repaired and then circuit No. 465 should again be checked for proper signal. The short to ground could have damaged ECM.
3. If test light on circuit No. 465 does light for 2 seconds, then ECM is supplying proper signal to energize fuel pump relay. If test light on circuit No. 139 does not light, an open must exist in circuit Nos. 139 or 3.
4. If test light on circuit No. 139 does light, then fuel pump relay is receiving 12 volts. Now determine if relay is receiving a good ground from ECM through circuit No. 497. If test light between circuit Nos. 139 and 497 will not light with ignition on, then check circuit No. 497 for an open between ECM and relay. If circuit No. 497 is okay, check for faulty ECM connector or faulty ECM.
5. If test light does light, then good ground is present. Check for continuity in circuit No. 120. If test light between circuit Nos. 139 and 120 will not light with ignition on, then circuit No. 120 must be repaired for an open. If test light lights, then fuel pump relay is failing to close and should be replaced.
   Fig 1: Hard or Intermittent Trouble Code E20

   
   Fig 2: Hard Or Intermittent Trouble Code E20

   
6. If fuel pump fuse is blown, it will be necessary to determine cause of excessive current draw. Engine data parameter P.1.0 uses fuel pump feedback signal as source of voltage. With voltage applied to circuit No. 120 through test light, a 0 voltage reading on diagnostic display would indicate a short to ground in system. If display reads 0 volts, raise vehicle and disconnect 6-way connector at fuel tank and note parameter value.
7. If display reads 0 volts, a short still exists. If voltage is displayed after removing oil pressure switch connector, switch must be shorted and should be replaced. If it remains at 0 volt reading, short is in circuit No. 120.
8. If display now reads more than 0 volts, check wiring between 6-way connector and fuel pump for short to ground. If wiring is okay, fuel pump must be inspected for short to ground.
9. If display of parameter P.1.0 did not read 0 volts at beginning of procedure, then short to ground is either in fuel pump relay, oil pressure switch, or wiring harness. If test light on circuit No. 139 does not light, fuel pump relay must be shorting to ground and should be replaced. If test light does light, short still exists. If light goes out after removing oil pressure switch connector, switch is shorted and should be replaced. If test light does light, short to ground is in circuit No. 139.