General Motors — Fuel Injector Coil Test
Testing & diagnosis · Fuel Injectors
From a General Motors service manual — check it applies to your exact model before use.
Before you start
- Be careful not to flood a single cylinder
Procedure
- Turn the ignition OFF and relieve the fuel pressure
- Access the fuel injector electrical connectors as required
- Connect the J 39021 fuel injector tester to B+ and ground
- Set the amperage supply selector switch to the Coil Test 0.5 amp position
- Connect the leads from the DMM to the fuel injector tester and set the DMM to the tenths scale (0.0)
- Connect the fuel injector tester to a fuel injector using the J 39021-380 injector test adapter
- Press the Push to Start Test button on the fuel injector tester
- Observe the voltage reading on the DMM and record the lowest voltage after the first second
- Repeat steps 8 through 11 for each fuel injector
- Replace the faulty fuel injectors if any reading is outside 5.7-6.6 V or is erratic
Tools required
- J 39021 Fuel Injector Coil and Balance Tester Amazon
- J 39021-380 Fuel Injector Test Harness Amazon
- Digital Multimeter Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Fuel injector resistance: 11.8-12.6 Ohms
- Voltage specification at 10-35°C (50-95°F): 5.7-6.6 V
Source: General Motors service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.