PFI Engines
Measure resistance of injector banks between test pins No. 37 and 58 (Right or rear) or 59 (Left or front) at breakout box. Record resistance. Refer to CAR - INJECTOR BANK RESISTANCE table.
Go to next step.
Connect test light between test pins No. 37 and 58 at the breakout box. Connect light between test pins No. 37 and 59 at breakout box.
Visually inspect, fuel injector "O" rings, fuel pressure regulator, and fuel rails. If there is a visible leak, remove pressure gauge. Repair leak as necessary. Rerun QUICK TEST. If there is no leak, go to next step. Fuel delivery system is okay. Problem is in common area for all cylinders, such as, vacuum leak, fuel contamination, or EGR leak.
8) Injector Balance Test Connect tachometer to engine. Start and run engine at idle. Disconnect and reconnect injectors one at a time. Note RPM drop for each injector. Each injector should produce a momentary RPM drop of about 100 RPM. Note that ISC will attempt to re-establish correct RPM. If each injector does not produce at least 100 RPM drop when disconnected, service or replace faulty injector(s) and repeat QUICK TEST. If RPM drop is correct for all injectors, fuel delivery is okay. Problem is in area common to all cylinders such as a vacuum leak, fuel contamination, EGR, or HEGO ground. Check MAP frequency, etc.
9) Cylinder Balance Test: Sequential PFI Engines ONLY Perform KOER Self-Test. After last code is displayed, wait 5-10 seconds. Enter CYLINDER BALANCE TEST by briefly opening throttle for one second (not WOT). Test time is approximately 2-3 minutes. A Code 77 indicates that the throttle was touched when the test was running and that the test was not completed. Use table to interpret codes received from test. If balance test does not display Code 90, go to step 4). If balance test displays Code 90 (Pass), fuel delivery is okay, fault is in an area common to all cylinders (except vehicles with Codes 41/91 or 42/92). Vehicles with Code 41 or 91 displayed, go to next step. If a Code 42 or 92 is displayed, go to step 23)
| Service Code | Cylinder or Injector No. | Breakout Box Test Pin No. |
|---|---|---|
| 90 | (Pass) | (Pass) |
| 10 | 1 | 58 |
| 20 | 2 | 59 |
| 30 | 3 | 12 |
| 40 | 4 | 13 |
| 50 | 5 | 14 |
| 60 | 6 | 15 |
| 70 | 7 | 42 |
| 80 | 8 | 52 |
| 77 | (Retest) | (Retest) |
11) Code 41 or 91: Fuel Control Always Lean If vehicle is equipped with dual HEGOs, Code 41 refers to the Right (rear) HEGO and Code 91 refers to the Left (front) HEGO. Run engine at 2000 RPM for 2 minutes. Turn key off and wait 10 seconds. Rerun KOER Self-Test. Check for Code 41 or 91. If Code 41 or 91 is not displayed, go to step 20). If Code 41 or 91 is displayed, go to appropriate step number as listed below.
- Engines equipped with MAP sensors: Go to next step.
- Engines equipped with MA meters: Go to step 14).
12) Checking HEGO Sensor on Engines With MAP Sensors Turn key off and set DVOM on 20-volt scale. Disconnect appropriate HEGO sensor from vehicle harness. Connect DVOM to HEGO SIGNAL lead at sensor and engine ground. Apply 10-14 in Hg to Manifold Absolute Pressure (MAP) sensor and start engine. Run engine at 2000 RPM for 2 minutes. If reading is greater than 0.5 volt, go to step 15). If reading is less than 0.5 volt, replace HEGO sensor, reconnect MAP, and rerun QUICK TEST.
14) Check HEGO Sensor on Engines With MA Sensor The purpose of this test is to verify HEGO sensor can generate a voltage signal of greater than 0.5 volt during KOER Self-Test. With key off and DVOM set on 20-volt scale and disconnect HEGO sensor from harness.