Engine Controls - Tests W/codes - Eec 2.5L: Other Ford Probe II

Hard Failures

Hard failures cause Malfunction Indicator Light (MIL) to come on and trouble codes to be set in Powertrain Control Module (PCM) memory. Trouble code remains until problem is repaired. To retrieve trouble codes, see READING SELF-DIAGNOSTIC CODES. Use circuit tests to determine cause of malfunction.

If a sensor fails, PCM will use a substitute value in its calculations to continue engine operation. PCM can estimate failed sensor values based on feedback from working sensors. In this condition, known as Limited Operating Strategy (LOS), vehicle runs but driveability will not be optimum.

Intermittent Failures

Intermittent failures may cause Malfunction Indicator Light (MIL) to flicker or glow. Light will go out after intermittent fault goes away. These faults indicate that a defect may or may not be present at time of testing, however corresponding trouble code will be retained in PCM memory.

If related fault does not reoccur within a certain time frame, trouble code will be erased from PCM memory. Intermittent failures may be caused by a sensor, connector or wiring problems. See INTERMITTENTS in TESTS W/O CODES - EEC 2.5L article in the ENGINE PERFORMANCE section.

Visual Check & Vehicle Preparation

Before hooking up any equipment to diagnose EEC system, visually check following and perform preparation procedures

1. Perform all necessary safety precautions to prevent personal injury or vehicle damage.
2. Block drive wheels. Set parking brake. Place shift lever in Park(A/T) or Neutral (M/T). DO NOT move shift lever during test unless specifically directed to do so.
3. Check condition of air cleaner and air ducting.
4. Check all vacuum hoses for leaks, restrictions and proper routing.
5. Check EEC system wiring harness connections for corrosion, damaged pins, loose wires and improper routing.
6. Check PCM, sensors and actuators for physical damage.
7. Check engine coolant and oil level.
8. Check battery condition. Turn off all lights and accessories. Ensure vehicle doors are closed when measuring voltage.
9. Ensure engine is at operating temperature.
10. Check exhaust system for leaks.

EQUIPMENT HOOKUP

Note. After performing equipment hookup, follow appropriate quick test procedures based on type of equipment being used. See QUICK TEST.

Using Analog Volt-Ohmmeter (VOM)

1) Turn ignition off. Locate Data Link Connector (DLC). see scheme 1and see scheme 2. Connect positive (+) lead of VOM to PCM STO terminal at DLC and negative (-) test lead to engine ground (GND). (Scheme 138) Set VOM to 0-20V DC range.

2) Connect a jumper wire between ground and PCM STI terminal of DLC. (Scheme 138)

Using Malfunction Indicator Light (MIL)

Check MIL operation. Turn ignition on. If MIL is on, MIL circuit is okay. Go to next step. If MIL is off, go to CIRCUIT TEST MIL. After performing CIRCUIT TEST MIL, return to this procedure. Connect a jumper wire between ground and PCM STI terminal of DLC. (Scheme 138)

Using Super Star II Tester

1) Turn ignition off. Connect color-coded adapter cable leads to Super Star II tester. Connect service adapter cables to vehicle Data Link Connector (DLC). (Scheme 138)

2) Connect Super MECS Adapter (007-00049 or 007-00052) between adapter cables and vehicle DLC. Slide adapter switch to EEC/MECS position. Slide Super Star II tester switch to EEC/MECS position.

Using New Generation Star Tester

1) Turn ignition off. Connect power cable and data cable to scan tester. Connect Rotunda Super MECS Adapter (007-00052) to scan tester data cable.

2) Plug matching connector on Super MECS adapter into vehicle DLC. Slide switch on Super MECS adapter to PCM position. Plug power cable on scan tester into cigar lighter or use battery adapter.

Scheme 138

Using Analog VOM

Watch voltmeter and count needle sweeps (between 0-12 volts) to determine code. Pay careful attention to length of pauses in order to read codes correctly. A 2-second pause occurs between digits in a code. A 4-second pause occurs between each code. (Scheme 139)

Using MIL/CHECK ENGINE light

Service codes are displayed as flashes. Code flashes are read in the same manner as with using an analog VOM.

Using New Generation Star or Super Star II Scan Tester

Codes will be displayed digitally. KOEO codes include hard and intermittent failures. To determine failure type (hard or intermittent), record and clear codes stored in PCM memory. Operate vehicle, and repeat KOEO self-test. Codes that reappear immediately are hard failures. Codes that do not reappear are intermittent failures.

Repair hard failures in order of code appearance before performing KOER self-test. Use appropriate CODE REFERENCE table to determine circuit test to perform. Clear codes from PCM memory after they have been recorded and/or faults have been repaired. See CLEARING CODES. When performing quick test, if no trouble codes are found during KOEO self-test, proceed to KOER self-test.

Scheme 139

CLEARING CODES

To clear trouble codes, deactivate self-test by disconnecting jumper wire from PCM STI terminal at Data Link Connector (DLC). Disconnect negative (-) battery cable. Depress brake pedal for 5-10 seconds. All hard codes and intermittent codes will be erased from PCM memory.

Analog VOM Or MIL

1) To perform Key On Engine Off (KOEO) test, turn ignition on and observe voltmeter (or MIL). Count voltmeter needle sweeps (or MIL flashes). If codes are not present, go to step 3). If codes are present, record codes, turn ignition off and go to next step.

Note. If code repeats immediately it is considered a "hard fault". If code does not immediately repeat the fault is intermittent and is not failing during self-testing.

2) Erase codes from PCM memory. See CLEARING CODES. Repeat step 1). If no codes are present go to next step. If any codes are present, refer to appropriate CODE REFERENCE table to determine circuit test to perform. After performing repair, return to start of quick test.

3) To perform Key On Engine Running (KOER) test, remove jumper wire from DLC. Start engine and run at 3000 RPM for 3 minutes. Reconnect jumper wire at DLC and read codes. If no codes are present, go to ANALOG VOM OR MIL under SWITCH MONITOR TEST. If codes are present, refer to appropriate CODE REFERENCE table to determine circuit test to perform. If engine does not start, check for codes and repair as necessary. If engine does not start and no codes are present, go to BASIC TESTING - V6 article in the ENGINE PERFORMANCE section below.

Super Star II Tester

1) To initiate KOEO self-test, depress center button to TEST position. Turn Super Star II tester on. Tester should display 888 for 2 seconds when activated. Turn ignition on.

2) Release and then depress center button to TEST position. After all codes have been received by tester, release center button.

3) Read and record all codes in tester memory, and then go to next step. If no code exists, go to step 5).

4) Erase codes from PCM memory. See CLEARING CODES. Repeat steps 1) and 2). If code does not reappear, fault is intermittent. Go to next step to begin KOER self-test. If code reappears, indicating hard fault, repair fault as necessary. Refer to appropriate CODE REFERENCE table to determine circuit test to perform. After performing repair, return to beginning of QUICK TEST. Repeat quick test until no hard codes exist.

5) To initiate KOER self-test, ensure center button on Super Star II tester is released and tester is OFF. Start and run engine at 2000 RPM for 3 minutes to ensure HO2S/O2S sensor is operating. Turn Super Star II tester on. Depress center button. Turn ignition off. Start engine and allow it to idle.

6) To activate KOER self-test, release and then reset center button to TEST position. Record all codes displayed. Refer to appropriate CODE REFERENCE table to determine circuit test to perform. If no code is displayed, go to SUPER STAR II TESTER under SWITCH MONITOR TEST.

New Generation Star Tester

See manufacturer's instructions provided with tester.

CODE REFERENCE

1) Turn engine off and allow to cool. Turn all accessories off. Disconnect PCM STI jumper from ground. Place shift lever in Park (A/T) or Neutral (M/T).

2) Reconnect jumper wire between ground and PCM STI terminal at DLC connector. Using VOM, connect positive (+) lead to SML terminal at DLC connector. (Scheme 138) Connect negative (-) lead to engine ground.

3) Turn ignition on. Operate input switches individually while watching VOM (or MIL). See SWITCH MONITOR TEST SPECIFICATIONS table. Ensure input switch is deactivated after each test. Leaving switch on while testing another switch may produce false results and cause misdiagnosis.

4) If input switch fails test (reading on VOM is not as specified or MIL does not blink), perform related circuit test. See SWITCH MONITOR TEST SPECIFICATIONS table. If all input devices fail, check Switch Monitor Light (SML) circuit. See CIRCUIT TEST SML. If all input devices test okay and no code is stored in PCM memory, EEC self-diagnostic system test is complete.

SWITCH MONITOR TEST SPECIFICATIONS

1) Turn engine off and allow it to cool. Turn all accessories off. Connect tester. See SUPER STAR II TESTER under QUICK TEST. Ensure tester center button is released.

2) Place shift lever in Park (A/T) or Neutral (M/T). Turn ignition on. Turn tester on, and set center button to TEST position. Observe LED indication as each input switch is tested. See SWITCH MONITOR TEST SPECIFICATIONS table.

3) Operate each switch individually. Turn off after test. Leaving switch on while testing another switch may produce false results and cause misdiagnosis. If input switch circuit fails test (reading on Super Star II tester is not as indicated), perform related circuit test. See SWITCH MONITOR TEST SPECIFICATIONS table.

4) If all input devices fail, check Switch Monitor Light (SML) circuit. See CIRCUIT TEST SML. If all input devices test okay and no code is stored in PCM memory, EEC system test is complete.

See manufacturer's instructions provided with tester.

CIRCUIT TESTS

Note. For identification of PCM connector terminals (Scheme 140)

Scheme 140

HOW TO USE CIRCUIT TESTS

1) DO NOT perform any circuit test unless specifically instructed by a procedure under QUICK TEST or SWITCH MONITOR TEST. Ensure all non-EEC related faults are corrected. Follow each test step in order until fault is found. When more than one code is received, start with first code displayed.

2) Use circuit tests to check electrical circuits before replacing sensors or any other components. Always test circuits for continuity between sensor and PCM. Test all circuits for short to power, opens or short to ground.

3) DO NOT connect any test light or measure voltage or resistance at PCM unless specified in testing procedure. DO NOT pierce wiring. If backprobing is specified, always backprobe harness side of connector. DO NOT probe connector side.

4) Isolate both ends of circuit and turn ignition off whenever checking for shorts or continuity, unless specified otherwise. Disconnect solenoids and switches before checking circuit continuity or energizing solenoids.

Solenoid Performance Check

To properly diagnose solenoid, check it in ON and OFF positions. When test procedure requires click test, check appropriate solenoid as follows.

1. BANK/INJ Install breakout box. Connect PCM to breakout box. Turn ignition on. Injectors should click when engine is cranked.
2. CANP Install breakout box, leaving PCM disconnected. Turn ignition Apply vacuum to vacuum nipple of canister purge solenoid. Using jumper wire, ground CANP test pin at breakout box. Vacuum should release.
3. EGRC Install breakout box, leaving PCM disconnected. Turn ignition Apply vacuum to hose from intake manifold, vacuum should hold. Using jumper wire, ground ERGC test pin of breakout box. Vacuum should release.
4. EGRV Install breakout box, leaving PCM disconnected. Turn ignition Apply vacuum from EGR valve. Vacuum should not hold. Using jumper wire, ground EGRV test pin of breakout box. Apply vacuum to EGR valve. Vacuum should hold.
5. FPRC Install breakout box, leaving PCM disconnected. Turn ignition Apply vacuum to FPRC solenoid. Vacuum should hold. Using jumper wire, ground FPRC test pin of breakout box. Vacuum should release.
6. HSIA Install breakout box, leaving PCM disconnected. Turn ignition Apply vacuum to HSIA solenoid. Vacuum should hold. Using jumper wire, ground HSIA test pin of breakout box. Vacuum should release.
7. IAC Install breakout box, leaving PCM disconnected. Turn ignition Using jumper wire, ground IAC test pin of breakout box intermittently. IAC solenoid should click when test pin is grounded.
8. VRIS Disconnect vacuum hoses at solenoid. Verify airflow between ports on solenoid. See VACUUM SPECIFICATION (VRIS SOLENOID) table. Install breakout box, leaving PCM disconnected. Turn ignition on. Using jumper wire, ground VRIS test pin of breakout box. Verify airflow between ports on solenoid.

VACUUM SPECIFICATIONS

Switch Performance Check

Switch must be checked in ON (closed) and OFF (open) positions. Switch should function as follows

1. ACS Switch is closed when A/C is on and blower is operating.
2. BLMT Switch is closed with fan selector switch in 3rd or HI position.
3. CCPS Switch is closed with A/C on and system pressure within normal operation range.
4. HPS Switch is closed with A/C on and system pressure exceeding normal operating range.
5. IDL Switch is open when throttle is depressed.
6. CPP/PNP CPP switch is closed when clutch pedal is depressed. PNP switch is closed when transaxle is in Neutral.
7. PSP Switch is closed when system pressure is high (turn steering wheel sharply with engine on).
8. WOT Switch is closed when throttle is open.

Check switch in ON and OFF positions. Install breakout box, leaving PCM disconnected. Turn ignition on. Measure voltage between breakout box test pin of switch being tested and ground. Switch should function as follows

1. BOO Depress brake pedal to close switch. Battery voltage should be present.
2. DEF Turn rear defroster on to close switch. Battery voltage should be present.
3. HDLT Turn headlight on to close switch. Battery voltage should be present.
4. VST Switch is closed when engine is cranking. About 9 volts should be present.

TP Sensor Circuit & Connector Terminal ID (TP2 - 2.5L). Scheme 141

Note. Enter this test only when a Code 12 is displayed during self-test procedures (KOEO or KOER) or when directed here from another circuit test. To prevent replacement of good components, check following non-EEC components for fault: idle speed or throttle stop adjustments, throttle shaft or linkage, and cruise control linkage.

CIRCUIT PIN IDENTIFICATION

1) Check System Integrity Visually check all wiring, connectors and components for evidence of damage, shorting or looseness. If fault is found, repair as necessary. If no fault is found, go to next step.

2) Check TP Sensor Signal Turn ignition off. Install breakout box. Install PCM to breakout box. Turn ignition on. Measure voltage at TP test pin at breakout box. Slowly depress accelerator pedal, and compare voltage to specifications shown in VOLTAGE & RESISTANCE SPECIFICATIONS (TP SENSOR) table. If voltage is as specified, and no other problem or code is found, replace PCM. If voltage is not as specified, go to next step.

3) Check VREF Turn ignition off. Disconnect TP sensor connector. Turn ignition on. Measure voltage at VREF terminal of TP sensor connector. If voltage is 4.5-5.5 volts, go to step 5). If voltage is not 4.5-5.5 volts, go to CIRCUIT TEST VREF.

4) Check TP Ground Turn ignition off. Disconnect TP sensor connector. Measure resistance between ground and GND terminal at TP sensor connector. If resistance is less than 5 ohms, replace TP sensor. If resistance is 5 ohms or more, repair open GND wire between ground and TP sensor.

VOLTAGE & RESISTANCE SPECIFICATIONS

Power Relay Ckt. & Connector Terminal ID (VPWR - 2.5L). Scheme 142

Power Relay Ckt. & Connector Terminal ID (VPWR - 2.5L). Scheme 143

Note. Enter this test only when directed here by other circuit tests. To prevent replacement of good components, check for faults in following non-EEC components: ignition switch, alternator, battery cables, ground straps and voltage regulator. This test is only intended to diagnose following circuits: VPWR and GND.

CIRCUIT PIN IDENTIFICATION

1) Check Circuit Integrity Visually check all wiring, connectors and components for evidence of damage, shorting or looseness. If fault is found, repair as necessary. If no fault is found, check battery voltage and charge condition. Service as necessary, and go to next step.

2) Check VPWR To PCM Turn ignition off. Install breakout box, leaving PCM disconnected. Turn ignition on. Measure voltage at VPWR test pin at breakout box. If voltage is more than 10 volts, go to next step. If voltage is 10 volts or less, go to step 4).

3) Check PCM Grounds Turn ignition off. With breakout box installed and PCM disconnected, measure resistance between ground and each GND test pin at breakout box. If all resistances are less than 5 ohms, VPWR circuit is okay. Return to circuit test that sent you here. If one or more resistances is 5 ohms or more, repair open in GND wire(s).

4) Check VPWR Wire From Main Relay To PCM Ensure ignition is off, breakout box is installed and PCM is disconnected. Remove main relay. Relay is located inside engine compartment fuse/relay box. Measure resistance between VPWR test pin at breakout box and VPWR at main relay connector. If voltage is less than 5 ohms, go to next step. If voltage is 5 ohms or more, repair open VPWR wire.

5) Check Ground At Main Relay Turn ignition off. Remove main relay. Measure resistance between ground and GND terminal at main relay connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open main relay ground wire.

6) Check Voltage At Main Relay Turn ignition off. Measure voltage at BATT terminal at main relay connector. If voltage is more than 10 volts, go to next step. If voltage is 10 volts or less, check 30-amp F/P INJ fuse. Fuse is located in engine compartment fuse/relay box. Replace fuse if blown. If fuse is okay, repair wire between fuse and main relay.

7) Check Power To Main Relay With main relay removed, turn ignition on. Measure voltage at PWR terminal at main relay connector. If voltage is more than 10 volts, replace main relay. If voltage is 10 volts or less, check 15-amp ENGINE fuse. Fuse is located in instrument panel fuse block. Replace fuse if blown. If fuse is okay, repair PWR wire.

Identifying VREF Connector Terminals (VREF3 - 2.5L). Scheme 144

Note. Perform this test when a check for VREF has failed in a sensor input circuit test. This test is only intended to diagnose following circuits: VREF and SIG RTN.

CIRCUIT PIN IDENTIFICATION

1) Check System Integrity Visually check all wiring, connectors and components for evidence of damage, shorting or looseness. If fault is found, repair as necessary. If no fault is found, go to next step.

2) Check VREF At PCM Turn ignition off. Install breakout box. Connect PCM to breakout box. Turn ignition on. Measure voltage between VREF and GND test pins at breakout box. If voltage is 4.5-5.5 volts, go to next step. If voltage is not 4.5-5.5 volts, go to CIRCUIT TEST VPWR. If VPWR circuit is okay, replace PCM.

3) Check For VREF At Sensor Turn ignition off. Disconnect BARO, EVP, VAF, MC-VAF and TP sensor connectors (if equipped). Turn ignition on. Measure voltage at VREF wire at each disconnected sensor connector. If all readings are 4.5-5.5 volts, VREF circuit is okay. Return to circuit test that sent you here. If any reading is 10-12 volts, repair short to power in VREF wire(s). If any reading is zero volts, go to next step.

4) Check For Open VREF Wires Turn ignition off. With breakout box installed, disconnect PCM. Disconnect BARO, EVP, VAF, MC-VAF and TP sensors. Measure resistance between VREF test pin at breakout box and VREF terminal of sensor connectors. If all resistance readings are less than 5 ohms, go to next step. If any reading is 5 ohms or more, repair open in VREF wire(s).

5) Check For Short In VREF Wires Turn ignition off. With breakout box installed, disconnect PCM. Disconnect Transaxle Control Module (TCM). TCM is located in front of PCM. Measure resistance between ground and VREF test pin at breakout box. If all resistance readings are more than 10,000 ohms, repair GND wire at sensor. If any resistance reading is 10,000 ohms or less, repair short in wire in question.

Instrument Cluster Connector Terminal ID (VSS - 2.5L). Scheme 145

Note. Enter this test only when directed here by other circuit tests.

1) Check System Integrity Visually check all wiring, connectors and components for evidence of damage, shorting or looseness. If fault is found, repair as necessary. If no fault is found, go to next step.

2) Check VSS Input Signal Turn ignition off. Install breakout box, leaving PCM disconnected. Turn ignition on. Raise vehicle on hoist. Shift transmission to Drive. Measure voltage at VSS test pin at breakout box while spinning front tire. If voltage fluctuates between zero and 5 volts, VSS circuit is okay. Return to circuit test that sent you here. If voltage does not fluctuate between zero and 5 volts, go to next step.

3) Check For An Open VSS Wire Ensure ignition is off. Disconnect 14-pin instrument cluster connector. Measure resistance between VSS test pin at breakout box and VSS terminal at instrument cluster connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open VSS wire.

4) Check For Short VSS Wire Ensure ignition is off. With breakout box installed and PCM disconnected. Measure resistance between ground and VSS test pin at breakout box. If resistance is more than 10,000 ohms, test vehicle speed sensor. See SYSTEM/COMPONENT TESTS - EEC (2.5L) article in the ENGINE PERFORMANCE section. If resistance is 10,000 ohms or less, repair short to ground in VSS wire.

SUMMARY

If no hard fault codes are present, driveability symptoms exist or intermittent codes exist, see TESTS W/O CODES - EEC 2.5L article in the ENGINE PERFORMANCE section for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.

EEC Wiring Diagram (Probe 2.5L - 1 Of 3). Scheme 146

EEC Wiring Diagram (Probe 2.5L - 2 Of 3). Scheme 147

EEC Wiring Diagram (Probe 2.5L - 3 Of 3). Scheme 148