Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 584 (ENGINE CONTROLS - 3.4L (TROUBLESHOOTING & DIAGNOSIS))TROUBLESHOOTINGFUEL INJECTOR COIL TESTTEST DESCRIPTION
1999 GMC Forward Control 5.7 R, Automatic
Test Description
1999 GMC Forward Control 5.7 R, AutomaticSECTION Test Description
WARNING: This page is about a different car, the 2004 Pontiac Aztek and 2004 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.
The numbers below refer to the step numbers on the diagnostic table.
- 3: This step tests each fuel injector resistance within a specific temperature range. If any of the fuel injectors display a resistance outside of the specified value, replace the fuel injector.
- 4: This step determines if all of the fuel injectors are within 3 ohms of each other. If the highest resistance value is within 3 ohms of the lowest resistance value, then all of the fuel injector coil windings are OK.
- 6: This step determines if the ignition 1 voltage circuit under the intake plenum is causing the concern.
- 8: This step determines which fuel injector is faulty. After subtracting the highest and lowest resistance values from the average value, replace the fuel injector that has the greatest resistance difference from the average.
Fuel Injector Coil Test
| Step | Action | Values | Yes | No |
|---|---|---|---|---|
| Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module (PCM) Connector End Views |
||||
| 1 | Did you perform the Diagnostic System Check-Engine Controls? | - | Go to Step 2 | Go to Diagnostic System Check - Engine Controls |
| 2 | Observe the engine coolant temperature (ECT) with a scan tool. Is the ECT value within the specified range? |
10-32°C (50-90°F) | Go to Step 3 | Go to Step 4 |
| 3 |
|
11-14 Ω | Go to Step 5 | Go to Diagnostic Aids |
| 4 |
|
3 Ω | Go to Fuel Injector Balance Test with Special Tool or Fuel Injector Balance Test with Tech 2 | Go to Step 8 |
| 5 | Remove the upper intake manifold. Refer to Intake Manifold Replacement - Upper
in Engine Mechanical. Did you complete the action? |
- | Go to Step 6 | - |
| 6 | Measure the resistance of the ignition 1 voltage circuit between the multi-way connector and the affected fuel injector connector, with a DMM. Is the resistance more than the specified value? |
5 Ω | Go to Step 7 | Go to Step 9 |
| 7 | Repair the open or high resistance in the ignition 1 voltage circuit. Did you complete the repair? |
- | Go to Step 11 | - |
| 8 |
|
- | Go to Step 11 | - |
| 9 | Test for an intermittent and for a poor connection at the affected fuel injector. Refer to Testing for Intermittent Conditions and Poor Connections
in Wiring Systems. Did you find and correct the condition? |
- | Go to Step 11 | Go to Step 10 |
| 10 | Replace any fuel injectors that are out of the specified range. Refer to Fuel Injector Replacement
. Did you complete the replacement? |
11-14 Ω | Go to Step 11 | - |
| 11 | Operate the system in order to verify the repair. Did you correct the condition? |
- | System OK | Go to Step 2 |
RENDER: 1.0x
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.