Diagnostic Aids

Perform this test when directed by QUICK TEST. ECA uses adaptive fuel logic to compensate for normal variances in fuel system components. If fuel system appears to be too rich or too lean, adaptive fuel will make appropriate shift in fuel delivery calculations to compensate.

If possible, measure several known good MAP/BP sensors. Average voltage reading will be typical for location and day of testing. See MAP SENSOR VOLTAGE OUTPUT .

CIRCUIT TEST HA ACRONYMS

Acronym	Definition
HEGO	Heated Exhaust Gas Oxygen Sensor
KAM	Keep-Alive Memory
SEFI	Sequential Electronic Fuel Injection

1) Continuous Memory Codes 181, 183, 189 & 192: This test identifies areas which could cause HEGO sensor to detect excessive oxygen, resulting in adaptive fuel enriching system to compensate. Excessive oxygen will be detected with lean conditions and certain rich conditions. For models with dual HEGO sensors, a related fuel code from both HEGO sensors could indicate a problem common to all cylinders. If a code is present from only one HEGO, this may help isolate a problem or be an early indication of a common problem.

Code 183 Indicates single right or rear HEGO detected a problem and adaptive fuel rich limit has been reached at idle.
Code 192 Indicates left or front HEGO detected a problem and adaptive fuel rich limit has been reached at idle.
Code 181 Indicates single right or rear HEGO detected a problem and adaptive fuel rich limit has been reached.
Code 189 Indicates left or front HEGO detected a problem and adaptive fuel rich limit has been reached.

Ensure a pass Code (111) is retrieved during both KOEO SELF-TEST and KOER SELF-TEST . Whenever a repair is made, clear KAM. If driveability symptoms are not present, be aware of other temporary conditions which may have set this code, such as fuel contamination or vehicle is out of fuel. For SEFI models, go to step 2). For non-SEFI models, go to step 3).

2) Run Cylinder Balance Test Run KOER SELF-TEST . After last repeated code, wait 5-10 seconds then goose throttle lightly (not WOT). Cylinder balance test will be activated. If Code 90 is present, go to next step. If Code 90 is not present, go to step 35).

3) Check For Vacuum/Air Induction Leaks Check vacuum hoses, air induction system and EGR tube for leaks and damage. Repair if necessary. Clear KAM, and repeat QUICK TEST . If leak or damage is not found, go to step 4).

4) Check For Low Fuel Pressure Turn ignition off. Release fuel system pressure. Install fuel pressure gauge. Cycle ignition from OFF to RUN position twice. Observe KOEO fuel pressure. Start engine. Observe and record KOER fuel pressure. For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS article. If fuel pressure is within specification, go to step 5). If fuel pressure is not within specification, repair fuel system. Clear KAM, and repeat QUICK TEST .

5) Check System Ability To Hold Fuel Pressure With fuel pressure gauge installed, cycle ignition from OFF to ON position twice to pressurize fuel system (DO NOT start engine). If fuel pressure remains at specification for 60 seconds, go to step 6) (MAP/BP equipped vehicles) or step 7) (all other vehicles). If fuel pressure does not remain at specification for 60 seconds, repair fuel system as necessary. Clear KAM, and repeat QUICK TEST .

6) Check MAP/BP Frequency Turn ignition off. Connect MAP/BP tester to MAP/BP sensor. See Figure in CIRCUIT TEST DF. Turn ignition on. If MAP/BP voltage is within specification, go to step 7). See MAP SENSOR VOLTAGE OUTPUT . If voltage is not within specification, check wiring to MAP/BP sensor for corrosion and other damage. Repair as necessary. Clear KAM, and repeat QUICK TEST . If wiring is okay, replace MAP/BP sensor. Clear KAM, and repeat QUICK TEST.

7) Check For Proper Battery Voltage To Fuel Injectors Turn ignition on. Measure and record voltage across battery terminals. Disconnect any fuel injector harness connector. Measure and record voltage between VPWR circuit at fuel injector wiring harness connector and battery negative terminal. If both voltage readings are within one volt of each other, go to step 8). If voltage readings differ by more than one volt, fuel injectors are not getting correct voltage. Repair as necessary. Clear KAM, and repeat QUICK TEST .

8) Verify CANP Solenoid Is Not Stuck Closed Enter OUTPUT STATE CHECK. See ADDITIONAL SYSTEM FUNCTIONS . Disconnect hose to manifold vacuum at CANP solenoid. Check for blockage, and repair or replace hose as necessary. With outputs off, apply 16 in. Hg vacuum to manifold vacuum side of CANP. Apply throttle to cycle outputs on. If vacuum releases, reconnect vacuum hose to CANP and go to next step (thermactor-equipped vehicles) or step 21) (all other vehicles). If vacuum does not release, repeat this step to verify results. If vacuum now releases, go to next step (thermactor-equipped vehicles) or step 21) (all other vehicles). If vacuum will not release, replace CANP solenoid. Clear KAM, and repeat QUICK TEST .

9) Check Thermactor System For Upstream Air Leak Check thermactor air control and vacuum control valves. See I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section. If air control valve is operating properly, go to step 21). If air control valve is not operating properly, repair or replace valve as necessary. Clear KAM, and repeat QUICK TEST .

NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 9) to step 15). No test procedures have been omitted.

15) Continuous Memory Codes 179, 182, 188 & 191 This test identifies areas which could cause engine to run rich, resulting in adaptive fuel reducing system to compensate. For vehicles with dual HEGO sensors, a related fuel code from both HEGO sensors could indicate a problem common to all cylinders. If a code is present from only one HEGO, this may help isolate a problem or it may be an early indication of a common problem.

Code 182 Indicates single right or rear HEGO detected a problem and adaptive fuel lean limit has been reached at idle.
Code 191 Indicates left or front HEGO detected a problem and adaptive fuel lean limit has been reached at idle.
Code 179 Indicates single right or rear HEGO detected a problem and adaptive fuel lean limit has been reached.
Code 188 Indicates left or front HEGO detected a problem and adaptive fuel lean limit has been reached.

Ensure a pass Code (111) is received during both KOEO SELF-TEST and KOER SELF-TEST . Whenever a repair is made, clear KAM. For SEFI vehicles, go to step 16). For non-SEFI vehicles, go to step 17).

16) Run Cylinder Balance Test Run KOER SELF-TEST . After last repeated code, wait 5-10 seconds and then goose throttle lightly (not WOT). Cylinder balance test will be activated. If Code 90 is present, go to next step. If Code 90 is not present, go to step 35).

17) Check For Low Fuel Pressure Turn ignition off. Release fuel system pressure. Install fuel pressure gauge. Cycle ignition from OFF to RUN position twice. Observe KOEO fuel pressure. Start engine. Observe and record KOER fuel pressure. For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS article. If fuel pressure is within specification, go to step 18). If fuel pressure is not within specification, repair fuel system as necessary. Clear KAM, and repeat QUICK TEST .

18) Check System Ability To Hold Fuel Pressure With fuel pressure gauge installed, cycle ignition from OFF to ON position twice to pressurize fuel system (do not start engine). If fuel pressure remains at specification for 60 seconds, go to step 19) (MAP/BP-equipped vehicles) or step 20) (all other vehicles). If fuel pressure does not remain at specification for 60 seconds, repair fuel system as necessary. Clear KAM, and repeat QUICK TEST .

19) Check MAP/BP Frequency Turn ignition off. Connect MAP/BP tester to MAP/BP sensor. Turn ignition on. Refer to MAP SENSOR VOLTAGE OUTPUT . If voltage is not within specification, check wiring to MAP/BP sensor for corrosion or other damage. Repair if necessary. Clear KAM, and repeat QUICK TEST . If wiring is okay, replace MAP/BP sensor. Clear KAM, and repeat QUICK TEST. If MAP/BP voltage is within specification, go to step 20).

20) Check Throttle Body & Air Induction System Check throttle body and air induction system for contamination and obstruction. Repair if necessary. Clear KAM, and repeat QUICK TEST . If throttle body and air induction system are okay, check PCV valve and repair as necessary.

21) Check PCV Valve Turn ignition off. Remove and shake PCV valve. If PCV valve rattles freely when shaken, go to step 26). Replace PCV valve if it does not rattle. Clear KAM, and repeat QUICK TEST .

NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 21) to step 26). No test procedures have been omitted.

26) Check HEGO Heater Circuit Turn ignition off. Disconnect HEGO sensor(s). Measure resistance between IGNITION RUN circuit and PWR GND circuit at HEGO sensor connectors. Resistance should be 2 ohms (cold) or 35 ohms (hot). Set DVOM to 20-volt scale. Turn ignition on. Measure voltage between IGNITION RUN circuit and PWR GND circuit at HEGO sensor connectors. Voltage should be 10.5 volts. If HEGO circuit checks are within specification, go to step 27). If HEGO circuit check are not within specification, isolate problem and repair as necessary. Clear KAM, and repeat QUICK TEST .

27) Inspect HEGO Sensor For Contamination Remove HEGO sensor(s) from exhaust manifold. Visually inspect for contamination and other damage. If HEGO sensors appear okay, go to step 28) (models with EGR) or step 30) (models without EGR). If HEGO sensors are contaminated or damaged, replace HEGO sensor. Clear KAM, and repeat QUICK TEST .

28) Check EGR Vacuum Supply At Idle Disconnect vacuum line at EGR valve. Connect vacuum gauge to EGR vacuum line. Start engine, and let it idle. If vacuum reading is less than 2.5 in. Hg, go to step 29). If vacuum reading is 2.5 in. Hg or more, check EVR solenoid filter for obstructions. Repair as necessary. If EVR filter is okay, replace EVR solenoid. Connect all components, clear KAM, and repeat QUICK TEST .

29) Verify EGR Valve Is Fully Seated Inspect EGR valve to ensure proper seating. If EGR valve is fully seated, reconnect vacuum line to EGR valve and go to step 30). If EGR valve is not fully seated, service or replace EGR valve as necessary. Clear KAM, and repeat QUICK TEST .

30) Check Cooling System Ensure cooling system is in good condition and all components are operating properly. If cooling system is okay, go to step 35). If cooling system requires service, repair or replace as necessary. Clear KAM, and repeat QUICK TEST .

NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 30) to step 35). No test procedures have been omitted.

35) Check Ignition System Ensure ignition system is operating properly. Scope check engine to verify no abnormal primary or secondary ignition firing lines exist. If ignition system is operating properly, go to next step. If system is not operating properly, make necessary repairs. See IGNITION SYSTEMS in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section. Clear KAM, and repeat QUICK TEST .

36) Injector Flow Check Check fuel injector flow using Fuel Injector Tester (Rotunda 113-00001). If injector flow is okay, go to step 37). If injectors are restricted, clean or replace injectors as necessary. Clear KAM, and repeat QUICK TEST .

37) Check Cylinder Compression Check cylinder compression. See MECHANICAL INSPECTION in BASIC TESTING article in the ENGINE PERFORMANCE Section. If cylinder compression is not within specifications, repair or replace engine as necessary. Clear KAM, and repeat QUICK TEST . If cylinder compression is within specification, go to step 40).

NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 37) to step 40). No test procedures have been omitted.

WARNING: Following road test is an optional procedure. Follow all applicable safety procedures and traffic laws. This road test requires a driver and an assistant. Assistant should make measurements, observe changes and record notes. If this test is not performed, go to TESTS W/O CODES article in the ENGINE PERFORMANCE Section for other possible causes.

40) Road Test Vehicle Purpose of this test is to identify faults by monitoring certain controlled parameters while trying to recreate a driveability or MIL light symptom. To prepare for road test:

Install fuel pressure gauge.
Install MAP/BP tester.
Disconnect ECA 60-pin connector, install breakout box and reconnect ECA to breakout box.
Connect "T" vacuum gauge into manifold vacuum line.
Have DVOM, writing materials and appropriate schematics and pin voltage charts available.

With ignition on and negative lead of DVOM connected to battery negative terminal, ensure following signals are correct:

POWERS: KAPWR (pin No. 1) is more than 10.5 volts, VPWR (pins No. 37 and 57) is more than 10.5 volts and VREF (pin No. 26) is 4-6 volts.
GROUNDS: PWR GND (pins No. 40 and 60), SIG RTN (pin No. 46) and IGN GND (pin No. 16) are 0-.5 volt.
OPTIONAL GROUNDS: HEGO GND (pin No. 49), CSE GND (pin No. 20) and MAF RTN (pin No. 9 or 15) are 0-.5 volt.

Drive vehicle and attempt to induce symptom. Information provided by vehicle operator may help when trying to recreate symptom. When symptom occurs, assistant should observe and record changes in voltage signals. Information about symptom, operating condition value of voltage signal and any other information available should be recorded for analysis. If unable to duplicate symptom during road test, verify EEC-IV values are within acceptable range. After road test is completed, analyze results to locate and repair fault causing symptom. If problem cannot be identified, go to TESTS W/O CODES article in the ENGINE PERFORMANCE Section for other possible causes of symptom.