Test Z - By-Pass Air

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: engine temperature not up to operating temperature, engine over operating temperature, improper idle speed/throttle stop adjustment or cruise control linkage.

1. Turn key off. Connect engine tachometer and start engine. Disconnect Idle Speed Control (ISC) harness. If RPM drops or if engine stalls, go to next step. If not, go to step 3).
2. If EGR service codes 31, 32, 33 or 34 are displayed, go to KEY ON/ENGINE RUNNING CIRCUIT TEST MENU  table and perform appropriate test. If not, service next code. If codes 12 or 23 are displayed, go to next step.
3. Turn key off. Disconnect ISC harness. With DVOM on 200-ohm scale, measure resistance of ISC solenoid. If resistance is between 7 and 13 ohms, go to next step. If resistance is less than 7 ohms or more than 13 ohms, replace ISC solenoid and repeat QUICK TEST  .
4. With key off and ISC harness disconnected, set DVOM on 200,000-ohm scale. Measure resistance from either ISC pin to ISC solenoid housing. If reading is 10,000 ohms or greater, go to step 5). If reading is less than 10,000 ohms, replace ISC solenoid. Repeat QUICK TEST  .
5. Leave ISC harness disconnected. Turn key on, leaving engine off. Measure voltage between VPWR circuit at ISC harness and battery ground terminal. If reading is less than 10.5-volts, repair open in circuit and repeat QUICK TEST  . If reading is 10.5-volts or more, go to next step.
6. Turn key off and wait 10 seconds. Leave ISC harness disconnected. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. With DVOM on 200-ohm scale, measure resistance between test pin 21 and ISC circuit at ISC harness connector. If reading is 5 ohms or more, repair open circuit and repeat QUICK TEST  . If reading is less than 5 ohms, go to next step.
7. Turn key off and wait 10 seconds. Leave ISC harness disconnected. Install breakout box, leaving ECA disconnected. Set DVOM on 200,000-ohm scale. Measure resistance between test pin 21 and test pins 40, 46, and 60. If all readings are less than 10,000 ohms, repair short to ground and repeat QUICK TEST  . If any reading is 10,000 ohms or more, go to next step.
8. Turn key off and wait 10 seconds. Leave breakout box installed. Leave ECA and ISC solenoid disconnected. With DVOM on 200,000-ohm scale, measure resistance between test pin 21 and 37. If reading is less than 10,000 ohms, repair short to power and repeat QUICK TEST  . If reading is 10,000 ohms or more, go to next step.
9. With key off, connect ECA and ISC. Leave breakout box installed. With vehicle prepared for QUICK TEST  , set DVOM on 20-volt scale. Connect DVOM between test pin 21 and 40. Start engine and observe DVOM. If meter reading varies during QUICK TEST  , replace ISC and repeat QUICK TEST  . If meter reading does not vary during QUICK TEST  , go to next step.
10. Code 13 Displayed. Disconnect ISC harness. Connect tachometer and repeat ENGINE RUNNING SELF-TEST. Record service codes. If engine speed remains below 1500 RPM during test, replace ECA and repeat QUICK TEST  . If engine speed does not remain below 1500 RPM, check engine vacuum hoses for proper routing and/or bad connections. Use vehicle emissions label as a guide. Make sure curb idle is correct. Ensure throttle plates are fully closed and throttle linkage is not binding. Check that cruise control linkage is not binding. If no mechanical problems appear, replace ISC and repeat QUICK TEST  .
11. Turn key off and wait 10 seconds. Deactivate SELF-TEST. Start and run engine at 2000 RPM for 2 minutes, until inlet radiator hose is hot and pressurized. Turn key and wait 10 seconds. Perform ENGINE RUNNING SELF-TEST. If code 17 is still displayed, inspect throttle body and air inlet for contamination. Service as necessary. If okay, adjust curb idle speed and repeat QUICK TEST  . If code 17 is not displayed, service other codes as necessary.