EXPERTEC TSB (316520)

Publication date: 1994-03-07
Reference number: 316520

EXPERTEC TSB

TECHNICAL SERVICE BULLETIN

Reference Number(s): 316520

INFORMATION ON THE NEWLY - RELEASED OXYGEN SENSOR

Model(s): Chevrolet, Pontiac, Buick, Cadillac

Bulletin No.: (Chevrolet) 316520

(Pontiac) 316520

(Buick) 316520

(Cadillac) 316520 Date: 03/07/1994

SUBJECT

INFORMATION ON THE NEWLY RELEASED PRE-CATALYST OXYGEN SENSOR (O2S) DIAGNOSTICS FOR THE TECH 1 MASS STORAGE CARTRIDGE (MSC)

MODELS

1994 BUICK ROADMASTER 1994 CADILLAC DEVILLE, CONCOURS, ELDORADO, FLEETWOOD, SEVILLE 1994 CHEVROLET CAMARO, CAPRICE, CORVETTE 1994 PONTIAC FIREBIRD

APPLICATIONS

THE O2S DIAGNOSTIC TEST SUPPORTS THE FOLLOWING APPLICATIONS:

'94 4.6L L37 VIN 9

'94 4.6L LD8 VIN Y

'94 4.9L L26 VIN B

'94 5.7L LT1 VIN P (EXCEPT Y)

'94 5.7L LT5 VIN J

THE O2S TEST IS AVAILABLE WITH RELEASE 3.0 OF THE MSC POWERTRAIN APPLICATION. INFORMATION ON ADDITIONAL APPLICATIONS AND ENHANCEMENTS TO FUTURE VERSIONS OF THE O2S DIAGNOSTIC TEST THAT MAY BE RELEASED WITH SUBSEQUENT TECHLINE CD-ROM UPDATES CAN BE FOUND UNDER THE INFORMATION NEWS" OPTION ON THE TECHLINE SYSTEM'S MAIN MENU.

CONDITION

MISDIAGNOSIS OF OXYGEN SENSOR PERFORMANCE.

PURPOSE

THE O2S TEST PROVIDES ADDITIONAL INFORMATION WHEN DIAGNOSING PROBLEMS WHERE THE OXYGEN SENSOR IS SUSPECT. THE O2S TEST ASSISTS IN DETERMINING IF THE OXYGEN SENSOR SYSTEM IS OPERATING PROPERLY OR MALFUNCTIONING. WHEN THE TECH-1 O2S TEST FAILS, THE APPROPRIATE SERVICE MANUAL DIAGNOSTIC PROCEDURES AND INFORMATION SHOULD BE USED TO FIND THE CAUSE AND REPAIR THE SYSTEM MALFUNCTION.

DESCRIPTION

THE O2S TEST CAN BE PERFORMED BY SELECTING THE "F9: O2S SYSTEM" FROM THE POWERTRAIN "MISC TEST" MENU. THE O2S TEST IS DIVIDED INTO THE FOLLOWING THREE STAGES: VEHICLE SETUP, HEATER ELEMENT AND OPEN, LEAN/RICH AND VOLTAGE DROP (TRANSITION TIME) TEST.

PROCEDURE

STAGE ONE - VEHICLE SETUP THIS STAGE CONFIRMS THAT THE FOLLOWING PRECONDITIONS ARE SATISFIED:

WHETHER OR NOT VEHICLE IS EQUIPPED WITH A HEATED O2S
KEY ON AND ENGINE OFF
COOLANT TEMPERATURE WITHIN CALIBRATED RANGE
VEHICLE SPEED = ZERO
THROTTLE CLOSED THE ABOVE CONDITIONS MUST BE SATISFIED FOR THE TEST TO RUN.

STAGE TWO - HEATER ELEMENT TEST

A. ALLOWS THE OXYGEN SENSOR'S TEMPERATURE TO STABILIZE FOR 30 SECONDS.

B. CONTINUOUSLY READS THE OXYGEN SENSOR VOLTAGE FOR MOVEMENT AWAY

FROM THE REFERENCE VOLTAGE SUPPLIED BY THE POWERTRAIN CONTROL

MODULE (PCM).

C. DETERMINES THE CONDITION OF THE HEATER ELEMENT CIRCUITS.

STAGE THREE - OPEN, LEAN/RICH AND VOLTAGE DROP (TRANSITION TIME) TESTS

A. RUNS THE ENGINE FOR TWO MINUTES AT A SPECIFIED RPM TO HEAT

THE OXYGEN SENSORS AND ATTEMPT TO PURGE THE SYSTEM FROM

CARBON DEPOSITS.

B. COMMANDS ENGINE TO CLOSED LOOP.

C. TESTS FOR AN OPEN OXYGEN SENSOR CIRCUIT.

D. MODIFIES THE AIR-FUEL RATIO TO DETERMINE THE LEAN SETTING FOR THE

OXYGEN SENSOR DROP TEST.

E. MODIFIES THE AIR-FUEL RATIO TO DETERMINE THE RICH SETTING FOR THE

OXYGEN SENSOR DROP TEST.

F. PERFORMS THE OXYGEN SENSOR DROP TEST BY DETERMINING THE TRANSITION

TIME FROM THE HIGH THRESHOLD LIMIT TO THE LOW THRESHOLD LIMIT.

TEST RESULT SCREENS UPON COMPLETION, THE TECH-1 OXYGEN SENSOR TEST

WILL DISPLAY THE OVERALL TEST RESULTS. THIS INCLUDES BOTH THE

HEATER ELEMENT PORTION, IF RUN, AND THE OXYGEN SENSOR TESTS.

INDIVIDUAL TEST RESULTS CAN BE DISPLAYED BY PRESSING THE UP ARROW.

A "PASSED" RESULT MEANS THE OXYGEN SENSOR IS FUNCTIONING TO TEST SPECIFICATIONS FOR BOTH THE HEATER ELEMENT AND THE OXYGEN SENSOR TESTS. IF THE OXYGEN SENSOR TEST PASSED AND CODES ARE PRESENT ON THE VEHICLE, USE THE APPROPRIATE DTC FLOWCHART FOUND IN THE SERVICE MANUAL.
A "FAILED" RESULT MEANS ONE OF THE HEATER ELEMENT OR OXYGEN SENSOR TESTS FAILED. A FAILED RESULT DOES NOT NECESSARILY MEAN THE OXYGEN SENSOR IS BAD. USE THE UP ARROW KEY TO SCROLL THROUGH THE INDIVIDUAL TEST RESULT SCREENS UNTIL A FAILED MESSAGE APPEARS. THE HEATER ELEMENT CIRCUIT TEST RESULTS WILL SHOW, "INCONCLUSIVE", IF ONE OF THE OXYGEN SENSOR TESTS FAILS OR IF THE TEST WAS BYPASSED. THE FOLLOWING ARE THE MESSAGES AND THE COURSE OF ACTION THAT SHOULD BE FOLLOWED.
"HEATER ELEMENT CIRCUIT FAILED" THIS MESSAGE WILL APPEAR WHEN THE HEATER ELEMENT IS THE ONLY TEST THAT FAILED. FOR 5.7L LT1 (VIN P) APPLICATIONS, ADDITIONAL CIRCUIT INFORMATION IS AVAILABLE WITHIN THE SERVICE MANUAL SECTION 6E3, DTC 13 OR 63. FOR THE 4.6L (VIN 9 OR Y) AND 4.9L (VIN B), ADDITIONAL CIRCUIT INFORMATION IS AVAILABLE WITHIN THE SERVICE MANUAL SECTION 6E-B, EXCESSIVE EXHAUST EMISSION ODORS.
"OXYGEN SENSOR CKT. OPEN" THIS MESSAGE WILL APPEAR WHEN THE OXYGEN SENSOR VOLTAGE DOES NOT ADEQUATELY FLUCTUATE FROM THE REFERENCE VOLTAGE. IF THIS FAULT IS PRESENT, USE DIAGNOSTIC INFORMATION FOR DTC "OPEN CIRCUIT". FOR THE 5.7L (VIN P) APPLICATIONS, USE SERVICE MANUAL SECTION 6E3, DTC 13 OR 63. FOR THE 4.6L (VIN 9 OR Y) AND 4.9L (VIN B), USE SERVICE MANUAL SECTION 6E-A (DTC 13 OR 17). THE OXYGEN SENSOR'S RICH, LEAN AND DROP TESTS WILL ALSO FAIL BECAUSE OF AN OPEN CIRCUIT WHEN THIS CONDITION EXISTS.
"FAILED RICH TEST" THIS MESSAGE WILL APPEAR WHEN THE OXYGEN SENSOR FAILS TO REACH THE HIGH THRESHOLD VOLTAGE THROUGHOUT THE OXYGEN SENSOR TEST. IF THIS FAULT IS PRESENT, USE DIAGNOSTIC INFORMATION FOR DTC "LEAN EXHAUST INDICATED". FOR THE 5.7L (VIN P) APPLICATIONS, USE SERVICE MANUAL SECTION 6E3, DTC 44 OR
1. FOR THE 4.6L (VIN 9 OR Y) AND 4.9L (VIN B), USE SERVICE MANUAL SECTION 6E-A (DTC 42 OR 44). THE OXYGEN SENSOR'S DROP TEST WILL ALSO BE FAULTED WHEN THIS CONDITION EXISTS.
"FAILED LEAN TEST" THIS MESSAGE WILL APPEAR WHEN THE OXYGEN SENSOR FAILS TO FALL BELOW LOW THRESHOLD LIMIT THROUGHOUT THE OXYGEN SENSOR TEST. IF THIS FAULT IS PRESENT, USE DIAGNOSTIC INFORMATION FOR DTC "RICH EXHAUST INDICATED". FOR THE 5.7L (VIN P) APPLICATIONS, USE SERVICE MANUAL SECTION 6E3, DTC 45 OR
1. FOR THE 4.6L (VIN 9 OR Y) AND 4.9L (VIN B), USE SERVICE MANUAL 6E-A (DTC 43 OR 45). THE OXYGEN SENSOR'S DROP TEST WILL ALSO BE FAULTED WHEN THIS CONDITION EXISTS.
"DROP TEST FAILED" THIS MESSAGE WILL APPEAR WHEN THE OXYGEN SENSOR FAILS TO TRANSITION BETWEEN THE HIGH THRESHOLD AND THE LOW THRESHOLD LIMITS IN LESS THAN THE SPECIFIED TIME. IF THIS FAULT IS PRESENT AND ALL OTHER OXYGEN SENSOR READINGS ARE OK, THE OXYGEN SENSOR MAY BE AT FAULT.

FIGURES: 0

GENERAL MOTORS BULLETINS ARE INTENDED FOR USE BY PROFESSIONAL TECHNICIANS, NOT A "DO-IT-YOURSELFER". THEY ARE WRITTEN TO INFORM THOSE TECHNICIANS OF CONDITIONS THAT MAY OCCUR ON SOME VEHICLES, OR TO PROVIDE INFORMATION THAT COULD ASSIST IN THE PROPER SERVICE OF A VEHICLE. PROPERLY TRAINED TECHNICIANS HAVE THE EQUIPMENT, TOOLS, SAFETY INSTRUCTIONS AND KNOW-HOW TO DO A JOB PROPERLY AND SAFELY. IF A CONDITION IS DESCRIBED, DO NOT ASSUME THAT THE BULLETIN APPLIES TO YOUR VEHICLE, OR THAT YOUR VEHICLE WILL HAVE THAT CONDITION. SEE A GENERAL MOTORS DEALER SERVICING YOUR BRAND OF GENERAL MOTORS VEHICLE FOR INFORMATION ON WHETHER YOUR VEHICLE MAY BENEFIT FROM THE INFORMATION.