Engine Controls - Tests W/codes - 2.0L A/t: Other Mazda MX-6 I

KOEO & KOER Codes (Hard Faults)

These codes indicate faults are present at time of testing. A hard fault may cause CHECK ENGINE or Malfunction Indicator Light (MIL) to go on and remain on until fault is repaired. If KOEO or KOER codes are retrieved during KOEO SELF-TEST or KOER SELF-TEST, use DIAGNOSTIC TROUBLE CODE REFERENCE CHARTS to find correct testing and repair procedures.

Continuous Memory Codes (Intermittent Faults)

These codes indicate a fault that may or may not be present at time of testing. These codes are used to diagnose intermittent problems. Continuous Memory Codes are retrieved after KOEO SELF-TEST. Some codes may turn on MIL/CHECK ENGINE light. Corresponding intermittent fault trouble code will be retained in PCM memory. If fault does not reoccur within 40 warm-up cycles, PCM will automatically clear code.

After noting and/or repairing fault, clear codes from memory. See CLEARING CODES. Intermittent faults may be caused by a sensor, connector or wiring-related problem. See INTERMITTENTS in TESTS W/O CODES article in the ENGINE PERFORMANCE section.

RETRIEVING CODES

Diagnostic trouble codes are retrieved from EEC-IV system through Data Link Connector (DLC). Various methods and test equipment may be used to access these codes

1. Analog Volt-Ohmmeter (VOM)
2. Scan Tester
3. Malfunction Indicator Light (MIL)/CHECK ENGINE Light
4. STAR Series Tester

DATA LINK CONNECTOR (DLC) LOCATION

Separator Pulse

Single 1/2-second separator pulse is issued 6-9 seconds after last KOEO code. Continuous Memory Codes (soft faults) are then displayed 6-9 seconds after 1/2-second separator pulse.

Pass Codes

A Code 111 indicates no diagnostic trouble codes were recorded in that portion of test; system passes that portion of test. If Code 111 is not retrieved in KOEO SELF-TEST, codes retrieved during KOER SELF-TEST may not be valid. Code 111 (pass code) must be obtained in KOEO SELF-TEST. A Code 111-1-111 output during KOEO SELF-TEST indicates no KOEO code or Continuous Memory Code was recorded.

Continuous Memory Codes

These codes result from information stored by PCM during continuous self-test monitoring. Codes are displayed after separator pulse code in KOEO SELF-TEST. Use these codes for diagnosis only when KOEO SELF-TEST and KOER SELF-TEST result in Code 111 (pass code) and all steps under QUICK TEST are successfully completed. (A few codes are exceptions which may be checked after KOEO codes have been repaired). These codes indicate faults recorded within last 40 engine starts. Fault may or may not be currently present. See DIAGNOSTIC TROUBLE CODE REFERENCE CHART.

Fast Codes

At start of KOEO SELF-TEST and after Wide Open Throttle (WOT) request in KOER SELF-TEST, PCM outputs short bursts of information, known as FAST CODES, which were used by manufacturer during assembly. These codes contain the identical information as slow codes, but are transmitted at 100 times the normal rate. With most equipment (except Super Star II tester), these code bursts are not visible. An entire code sequence lasts less than 1/2 second.

Scheme 34

CLEARING CODES

To clear codes from PCM memory, start KOEO SELF-TEST. When diagnostic trouble codes appear on test equipment or MIL/CHECK ENGINE light, disconnect jumper wire from Self-Test Input (STI) connector. If using STAR Series Tester, unlatch center button. This procedure erases Continuous Memory Codes from PCM memory. If problem has not been corrected or fault is still present, hard code will immediately be reset in PCM memory.

VISUAL CHECK

Complete all steps in BASIC TESTING article in the ENGINE PERFORMANCE section before proceeding to self-diagnostic tests. Ensure all vacuum hoses and EEC-IV wiring harnesses are properly connected.

EQUIPMENT HOOKUP

Apply parking brake, and place shift lever in Park position. Block drive wheels. Turn off all electrical accessories. Connect appropriate test equipment to vehicle as follows

Analog Volt-Ohmmeter (VOM)

1) Turn ignition off. Set VOM at 0-15V DC range. Connect positive lead of VOM to positive battery terminal.

2) Connect negative VOM lead to Self-Test Output (STO) terminal of Data Link Connector (DLC). (Scheme 35) Go to KOEO SELF-TEST. Activate KOEO SELF-TEST by connecting jumper wire from Self-Test Input (STI) pigtail to signal return (SIG RTN) terminal at DLC with ignition on.

Scan Tester

Follow manufacturer's instructions to hook up equipment and record diagnostic trouble codes.

STAR Series Tester

Turn ignition off. Connect color-coded adapter cable leads to diagnostic tester. Connect 2 service connectors of adapter cable to vehicle Data Link Connector (DLC) and STI pigtail connector. Go to KOEO SELF-TEST.

CHECK ENGINE Light/Malfunction Indicator Light (MIL)

Turn ignition on. Connect a jumper wire between Self-Test Input (STI) pigtail and signal return (SIG RTN) terminal of Data Link Connector (DLC). (Scheme 35) Go to KOEO SELF-TEST.

Scheme 35

ADDITIONAL SYSTEM FUNCTIONS

Additional diagnostic system features are available to help diagnose driveability problems and service EEC-IV systems.

Malfunction Indicator Light (MIL)

MIL are intended to alert driver of certain malfunctions in EEC-IV system. Light may also be used to retrieve diagnostic trouble codes stored in PCM. When hooked up for KOEO SELF-TEST or KOER SELF-TEST, light will display all codes which turn on light during vehicle operation.

Light should come on when ignition is turned on and go out when engine is started. If light comes on and then goes off during vehicle operation, code causing light to come on will be stored in PCM memory as a Continuous Memory Code. If light comes on during vehicle operation, vehicle should be inspected as soon as possible. Immediately turning off engine is not necessary; vehicle can be driven with light on.

Output State Check

Output state check is used as an aid in servicing output actuators associated with EEC-IV system. It allows technicians to energize and de-energize most system output actuators on command. This mode is entered from KOEO SELF-TEST after all codes have been retrieved.

Disconnect cruise control servo (if equipped). With DVOM on 20-volt scale, connect DVOM negative lead to STO terminal at Diagnostic Link Connector (DLC). Connect positive lead to positive battery terminal. Using jumper wire, connect STI to SIG RTN at Diagnostic Link Connector (DLC).

Perform KOEO SELF-TEST until continuous memory test is complete. DVOM will read less than 1.0 volt when test is complete. Depress and release throttle. If voltage increases, OUTPUT STATE CHECK has been entered. If voltage does not increase, depress throttle to WOT and release. If STO voltage still does not increase, go to CIRCUIT TEST QC.

Failure Mode Effects Management (FMEM) Code 998

FMEM mode allows system operation when sensors fail or transmit signals that are out of normal operating range. During FMEM mode, PCM substitutes a mid-range signal for defective sensor while continuing to monitor sensor. If faulty sensor's signals return to normal operating range, PCM will use those signals. A Code 998 will be displayed when FMEM mode is in effect.

CIRCUIT TESTS

Note. A breakout box, connected to vehicle harness at PCM, is necessary to perform most circuit tests. References to Test Pin No. found in CIRCUIT TEST steps refer to test terminals on manufacturer's breakout box. Circuit diagrams at beginning of each test identify circuit and wire colors.

HOW TO USE CIRCUIT TESTS

1) Ensure all non-EEC related faults found while performing steps in BASIC TESTING article in the ENGINE PERFORMANCE section have been corrected. DO NOT perform any CIRCUIT TEST unless specifically instructed by a QUICK TEST procedure. Follow each test step in order until fault is found. DO NOT replace any part unless directed to do so. When more than one code is retrieved, start with first code displayed.

2) CIRCUIT TESTS ensure electrical circuits are okay before sensors or other components are replaced. Always test circuits for continuity between sensor and PCM. Test all circuits for short to power, opens or short to ground. Voltage Reference (VREF) and Voltage Power (VPWR) circuits should be tested with ignition on or as specified in CIRCUIT TESTS.

3) DO NOT measure voltage or resistance at PCM. DO NOT connect any test light unless specified in testing procedure. All measurements are made by probing rear of connector (wiring harness side). Isolate both ends of a circuit and turn ignition off when checking for shorts or continuity, unless instructed otherwise.

4) Disconnect solenoids and switches from harness before measuring continuity and resistance or applying voltage. After each repair, check all component connections and repeat QUICK TEST.

5) An open circuit is defined as a resistance reading of greater than 5 ohms. This specification tolerance may be too high for some items in EEC-IV system. If resistance approaches 5 ohms, always clean suspect connector and coat it with protective dielectric silicone grease. A short is defined as a resistance reading of 10,000 ohms or less, unless stated otherwise in CIRCUIT TEST.

Note. In following tests, circuit diagrams and illustrations are courtesy of Mazda Motors Corp.

CIRCUIT TESTS are grouped as follows

1. AA-C - No Start & Voltage Tests.
2. DA-DR - Input Sensor Tests.
3. FD-FF - Additional Input Component Tests.
4. G-J - Fuel Control Systems.
5. KD-TC - PCM (Processor) Output Tests.

Preliminary Instructions

Record and clear continuous memory codes. Warm engine to normal operating temperature. Place gear selector in Drive position. Accelerate hard to 35 MPH and coast down to a stop. Shut off engine. Perform KOEO SELF-TEST. Go to step 1).

1) Continuous Memory Code 452 Code 452 indicates PCM detected incorrect output from VSS sometime during vehicle operation. Possible causes for this code are

1. Faulty VSS.
2. Open or shorted circuit.
3. Faulty PCM.

Perform appropriate drive cycle procedure. See PRELIMINARY INSTRUCTIONS. Ensure driveability complaint can be verified. If Code 452 is still present or driveability complaint can be verified, go to next step. If code is not present or complaint cannot be verified, fault cannot be duplicated at this time. Clear codes, and see SYMPTOMS in TESTS W/O CODES article in the ENGINE PERFORMANCE section.

2) Check VSS Circuit Continuity Turn ignition off. Disconnect VSS sensor. Remove PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM connector disconnected. Measure resistance between VSS (+) terminal at VSS wiring harness connector and test pin No. 3 at breakout box. Also, measure resistance between VSS (-) terminal at VSS wiring harness connector and test pin No. 6 at breakout box. If any resistance reading is more than 5 ohms, repair open circuit in VSS wiring harness. Remove breakout box reconnect all components. Repeat step 1). If both resistance readings are 5 ohms or less, go to next step.

3) Check VSS Circuits For Shorts To Power Or Ground Turn ignition off. Ensure PCM and VSS are disconnected. Measure resistance between test pin No. 3 and test pins No. 6, 37 and 40 at breakout box. If all readings are more than 500 ohms, go to next step. If any reading is 500 ohms or less, repair shorts in VSS wiring harness and repeat step 1).

4) Check VSS Resistance Turn ignition off. Disconnect VSS wiring harness connector. Measure resistance between VSS terminals. If resistance is not 190-250 ohms, replace VSS and repeat step 1). If resistance is 190-250 ohms, replace PCM and repeat step 1).

Engine Starts

1. Fuel pump secondary circuit shorted to power.
2. Fuel pump relay contacts always closed.
3. Open Fuel Pump Monitor (FPM) circuit between PCM and junction to POWER-TO-PUMP circuit.
4. Faulty PCM.

No Start

1. IFS switch circuit open or not reset.
2. Open circuit in or between PCM and fuel pump.
3. Faulty ground connection at fuel pump.
4. Faulty fuel pump.

If engine starts, go to next step. If engine does not start, go to step 15).

11) Check Fuel Pump Operation Turn ignition on. Wait 5 seconds. Listen for fuel pump operation. If fuel pump is off, go to step 13). If fuel pump is on, go to next step.

12) Check For Fuel Pump Relay Always Closed Turn ignition off. Disconnect fuel pump relay. Turn ignition on. If fuel pump is off with relay disconnected, replace fuel pump relay and repeat QUICK TEST. If fuel pump is on with relay disconnected, repair short to power in POWER-TO-PUMP or FPM circuit. (For models with relay block, also check fuel pump prime plug circuit). Repeat QUICK TEST.

13) Check Continuity Of Fuel Pump Monitor (FPM) Circuit Turn ignition off. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Disconnect fuel pump relay. Measure resistance between test pin No. 8 at breakout box and POWER-TO-PUMP circuit at fuel pump relay wiring harness connector. If resistance is less than 5 ohms, replace PCM and repeat QUICK TEST. If resistance is 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components, and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 13) to step 15). No test procedures have been omitted.

15) Check IFS Switch Turn ignition off. Disconnect fuel pump IFS switch. Ensure switch is reset. Measure resistance of IFS switch. If resistance is less than 5 ohms, check for open in POWER-TO-PUMP circuit, poor fuel pump ground or faulty fuel pump. If resistance is 5 ohms or more, reset or replace IFS switch. Repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 15) to step 20). No test procedures have been omitted.

20) Code 543 Code 543 indicates fuel pump secondary circuit failure between B+ circuit and FPM connection to POWER-TO-PUMP circuit. Following are possible causes

1. Open circuit between B+ and FPM connection to POWER-TO-PUMP circuit.
2. Fuel pump relay contacts are always open.

1. Faulty PCM.

If engine starts, replace PCM and repeat QUICK TEST. If engine does not start, go to next step.

21) Check For B+ To Fuel Pump Relay Turn ignition off. Disconnect fuel pump relay. Measure voltage between B+ terminal at fuel pump relay wiring harness connector and negative battery terminal. If voltage is 10.5 volts or more, go to next step. If voltage is less than 10.5 volts, check fuse/fusible link. If fuse/fusible link is okay, repair open circuit in B+ circuit. Repeat QUICK TEST.

22) Check POWER-TO-PUMP Circuit Continuity Turn ignition off. Leave fuel pump relay disconnected. Measure resistance between POWER-TO-PUMP terminal at fuel pump relay wiring harness connector and negative battery terminal. If resistance is less than 10 ohms, replace fuel pump relay and repeat QUICK TEST. If resistance is 10 ohms or more, repair open circuit in POWER-TO-PUMP circuit between FPM junction and fuel pump relay. Reconnect fuel pump relay and repeat QUICK TEST.

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 22) to step 90). No test procedures have been omitted.

90) Continuous Memory Code 542 Code 542 indicates one of the following conditions

1. Faulty ground circuit at fuel pump.
2. FPM or POWER-TO-PUMP circuit short to power.
3. IFS switch not reset.
4. Fuel pump relay contacts stuck closed.
5. Open circuit in or between fuel pump and FPM circuit at PCM.
6. FUEL PUMP circuit is activated at a time that is not programmed into PCM strategy.
7. Engine stall due to excessive load.

Start engine. Check for engine miss or intermittent fuel pump deactivation while performing following

1. Shake and bend POWER-TO-PUMP circuit wiring harness connector between fuel pump relay and fuel pump.
2. Shake and bend fuel pump ground circuit between fuel pump and ground.
3. Lightly tap fuel pump to simulate road shock.
4. Lightly tap IFS switch to simulate road shock.

Turn ignition off. Check fuel pump harness connector and fuel pump ground for corrosion and damage. Isolate and repair any faults. Clear continuous memory, and repeat QUICK TEST. If no faults are found, go to next step.

91) Check FPM Circuit Turn ignition off. Disconnect PCM 60-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving PCM disconnected. Connect test light between test pin No. 8 (No. 19 on Escort and Tracer) and test pin No. 37 at breakout box. With test light lit, perform wiggle test on FPM circuit between fuel pump and PCM. Light will go out if fault is found, indicating an open circuit. If a fault is found, repair as necessary. Remove breakout box, reconnect all components, and repeat QUICK TEST. If no fault is found, go to next step.

92) Check For Shorts To Power Connect a test light between breakout box test pin No. 8 and test pin No. 40. Test light should be off. Observe test light while bending and shaking FPM circuit and POWER-TO-PUMP circuit. Lightly tap fuel pump relay to simulate road shock. Fault is indicated if test light comes on. Isolate and repair fault as necessary, and repeat QUICK TEST. If no fault is found, go to step 99).

Note. A break in step numbering sequence occurs at this point. Procedure skips from step 92) to step 99). No test procedures have been omitted.

99) Road Test Vehicle Purpose of this test is to identify faults by monitoring certain controlled parameters while trying to recreate a drive-ability or MIL symptom. To prepare for road test

1. Install fuel pressure gauge.
2. Disconnect PCM 60-pin connector, install breakout box and reconnect PCM to breakout box.
3. Connect "T" vacuum gauge into manifold vacuum line.
4. Have DVOM, writing materials and appropriate schematics and pin voltage charts available.

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

1. POWERS: KAPWR (pin No. 1) is greater than 10.5 volts, VPWR (pins No. 37 and 57) is greater than 10.5 volts and VREF (pin No. 26) is 4-6 volts.
2. GROUNDS: PWR GND (pins No. 40 and 60), SIG RTN (pin No. 46) and IGN GND (pin No. 16) are 0.0-0.5 volt.
3. OPTIONAL GROUNDS: HO2S GND (pin No. 49), CSE GND (pin No. 20) and MAF RTN (pin No. 9 or 15) are 0.0-0.5 volt.

SUMMARY

If no diagnostic trouble code is present but driveability problem still exists, proceed to TESTS W/O CODES article in the ENGINE PERFORMANCE section for symptom diagnostic or intermittent diagnosis procedures.