Engine Controls - System/component Tests Acura SLX I

INTRODUCTION

Before testing separate components or systems, perform procedures in BASIC TESTING article. Since many computer-controlled and monitored components set a trouble code if they malfunction, also perform procedures in appropriate TESTS W/CODES article.

Note. Testing individual components does not isolate shorts or open circuits. Perform all voltage tests with a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure. Use ohmmeter and refer to WIRING DIAGRAMS to isolate shorted or open wiring harness.

CHART REFERENCE

POWERTRAIN CONTROL MODULE (PCM)

Note. To perform the following ground and power tests, use appropriate wiring diagram in WIRING DIAGRAMS article.

Ground Circuits

1. Disconnect PCM connectors. Using an ohmmeter, check for continuity to ground on PCM harness ground terminals. See PCM GROUND CIRCUIT TERMINALS table. Resistance should be zero ohms. If not, locate and repair open in wire.
2. Reconnect PCM connectors. Using a voltmeter, connect negative lead of voltmeter to a good ground. Backprobe positive lead of voltmeter to each ground terminal. With vehicle running, voltmeter should indicate less than one volt. If voltmeter reading is greater than one volt, check for open, short, corrosion or loose connection on ground circuit. Repair as necessary.

PCM GROUND CIRCUIT TERMINALS

Power Circuits

Turn ignition on. Using a voltmeter, backprobe PCM harness connectors. Check for battery voltage between PCM ignition power terminals and ground. See PCM BATTERY CIRCUIT TERMINALS table. If battery voltage is not present, check IGN fuse and fusible links. If fuse is okay, check for an open in wire between battery and ignition switch, and between ignition switch and PCM terminal. If okay, check for a defective ignition switch.

PCM POWER CIRCUIT TERMINALS

Engine Coolant Temperature (ECT) Sensor

If a coolant sensor-related code is present, see appropriate DTC in SELF-DIAGNOSTICS. An out-of-calibration sensor may not set a trouble code. Use following procedure to test sensor calibration. Disconnect ECT sensor connector. Measure resistance between sensor terminals. Resistance should be high when engine is cold and drop as engine warms. See ECT SENSOR RESISTANCE VALUES table.

ECT SENSOR RESISTANCE VALUES

Oxygen Sensor (O2S)

If an O2S related code is present, see appropriate DTC in SELF-DIAGNOSTICS.

Heated Oxygen Sensor (HO2S)

If an HO2S related code is present, see appropriate DTC in SELF-DIAGNOSTICS.

Intake Air Temperature (IAT) Sensor

If an IAT sensor-related code is present, see appropriate DTC in SELF-DIAGNOSTICS. An out-of-calibration sensor may not set a trouble code. Use following procedure to test calibration. Disconnect IAT sensor harness connector. Connect ohmmeter between sensor terminals. Sensor resistance should be as specified. See IAT SENSOR RESISTANCE table. With vehicle sitting overnight, IAT sensor and coolant sensor should have close to the same resistance reading.

IAT SENSOR RESISTANCE

Knock Sensor

Disconnect PCM harness connector. Using an ohmmeter, measure knock sensor resistance through knock sensor signal circuit. Resistance should be 90,000-110,000 ohms. Also see TIMING CONTROL SYSTEMS under IGNITION SYSTEM and appropriate DTC in SELF-DIAGNOSTICS.

Manifold Absolute Pressure (MAP) Sensor

An out-of-calibration sensor may not set a trouble code. Use following procedure to check sensor calibration. If driveability problems exist, MAP sensor failure is suspected and no MAP code is present, check MAP vacuum hose for splits, kinks, proper routing and blockage. Check voltage output range of MAP sensor. At idle, voltage should read 1 to 1.5 volts increasing between 4.5 to 4.8 volts at Wide Open Throttle (WOT). MAP sensor circuit malfunction should set a related code in PCM memory. If a code is present, see appropriate DTC in SELF-DIAGNOSTICS.

Mass Air Flow Sensor (MAF)(3.2L)

A MAF sensor malfunction will set a DTC. If a code is present, see appropriate DTC in SELF-DIAGNOSTICS.

Throttle Position (TP) Sensor

TP sensor circuit malfunction should set a related DTC. If so, see related G - TESTS W/CODES article. Also see TP SENSOR ADJUSTMENT in ON-VEHICLE ADJUSTMENTS.

Transmission Temperature Sensor

Disconnect transmission temperature sensor. Measure resistance across terminals of sensor connector. Replace sensor if resistance is not within specification. See TRANSMISSION TEMPERATURE SENSOR RESISTANCE table.

TRANSMISSION TEMPERATURE SENSOR RESISTANCE

Transmission Range (TR) Switch

A problem in transmission range switch circuit will set DTC(s). See appropriate DTC IN SELF-DIAGNOSTICS.

VEHICLE SPEED SENSOR (VSS)

Vehicles have one VSS located in vehicle speedometer and one mounted on rear of transmission. Transmission mounted VSS sends signal to speedometer VSS, which controls needle movement and sends signal to ECM and cruise control. A problem in VSS circuit will set DTC(s). See appropriate DTC in SELF-DIAGNOSTICS.

Ignition Control Module

See ENGINE CRANKS BUT WILL NOT RUN in BASIC DIAGNOSTIC PROCEDURES.

Idle Air Control

See IDLE CONTROL SYSTEM.

Horn Relay

Check for continuity between terminals No. 2 and No. 3. (Scheme 2) Continuity should not exist. Using jumper wires, apply battery voltage to terminal No. 1 and ground terminal No. 2. Continuity should exist between terminals No.2 and No. 3. If not as specified, replace relay.

Scheme 2

Main Relay

This 4-terminal relay is used for A/C, Fuel Pump and PCM power control. Test for continuity between terminal No.2 and No. 4, continuity should not exist. (Scheme 3) Apply battery voltage to terminal No. 1 and ground terminal No. 3. Continuity should exist between terminals No. 2 and No. 4. If not as specified, replace relay.

Scheme 3

FUEL DELIVERY

Note. For fuel system pressure testing, see BASIC DIAGNOSTIC PROCEDURES.

Fuel Pressure Regulator

Fuel pressure regulator is a vacuum-controlled diaphragm type, which uses manifold vacuum to modify fuel pressure to compensate for engine load fuel requirements.

Fuel Pump Relay

See FUEL SYSTEM in BASIC DIAGNOSTIC PROCEDURES.

Fuel Pump Relay By-Pass Procedure

If fuel pump will not energize, relay may be by-passed to test fuel pump. Turn ignition off. Using a fused jumper wire, apply battery voltage to fuel pump test connector. Fuel pump should turn on.

Fuel Injector(s)

Disconnect fuel injector harness connector. Measure resistance across injector terminals. Resistance should be as specified. See FUEL INJECTOR RESISTANCE table.

FUEL INJECTOR COIL RESISTANCE

Scheme 4

1. Perform On-Board Diagnostics (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in BASIC TESTING article. After performing OBD system check, go to next step.
2. Turn ignition off. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELEASE. Connect Fuel Injector Tester (J 39021-5V) to battery positive and ground, and Injector Switch Box (J 39021-90). Connect switch box to grey fuel injector harness connector located at front of EVAP canister bracket. Set amperage supply selector switch to Coil Test 0.5 amp position. Connect DVOM leads to fuel injector tester. (Scheme 4) Set DVOM to tenths scale. Observe ECT. If ECT is within 50-95 degrees (10-30 C), go to step 3). If ECT is not within specification, go to step 5.
3. Set injector switch box to injector No. 1. Press PUSH TO START TEST button of tester. Observe voltage reading (voltage may rise during test). Record lowest voltage observed after first second of test. Repeat procedure on all injectors. If any injector had large fluctuations in voltage that did not stabilize or voltage reading out of 5.7-6.6 volt range, go to step 4). If all within specification, go to step 7).
4. Replace faulty fuel injector(s). See FUEL RAIL & FUEL INJECTORS in REMOVAL, OVERHAUL & INSTALLATION. Go to step 7).
5. Set injector switch box to injector No. 1. Press Push To Start button on injector tester. Observe voltage reading (voltage may rise during test). Record lowest voltage after first second of test. Set injector switch box to next injector and repeat procedure to all injectors. If any injector had large fluctuations in voltage that did not stabilize or voltage reading above 9.5 volts, go to step 4). If all readings within specification, go to step 6).
6. Identify highest voltage reading recorded (below 9.5). Subtract voltage, from each injector, reading of each injector from highest voltage reading recorded. If subtracted value for any injector, is greater than 0.6 volts, go to step 4). If all within specification, go to applicable FUEL INJECTOR BALANCE TEST.

FUEL INJECTOR BALANCE TEST

Note. Allow engine to cool to avoid irregular readings due to "hot soak" fuel boiling. To prevent flooding, INJECTOR BALANCE TEST should not be repeated more than once without starting and running engine.

The injector balance test is used to pulse the injector for a precise amount of time, spraying a measured amount of fuel in the intake manifold. As each injector is pulsed, a drop in fuel rail pressure occurs. This pressure drop can be recorded and compared to other injectors. An injector with a pressure drop of 1.5 psi (10 kPa) or more, greater than or less than other injectors, should be considered faulty.

FUEL TANK LEAK CHECK

1. Relieve fuel system pressure. See FUEL SYSTEM PRESSURE RELEASE in REMOVAL, OVERHAUL & INSTALLATION. Remove fuel tank. Plug filler neck, vent hoses and fuel lines.
2. Install short piece of fuel line on fuel tank meter vent tube. Apply approximately 1-1.5 PSI (7-10 kPa) of air pressure to tank through vent tube. Test suspect area with soap solution or by submersion. If leak is found, replace tank.

Idle Air Control (IAC) Valve

Note. Functional testing of Idle Air Control (IAC) valve requires a bidirectional scan tool capable of cycling PCM output devices or a special IAC Driver and Noid Light Set (222L or J-37027).

1. Disconnect harness connector to motor. Check resistance across IAC coil terminals "A" to "B" and "C" to "D". Resistance should be 40-80 ohms. If okay, go to next step. If resistance is not as specified, replace IAC valve.
2. Check resistance between IAC terminals "B" to "C" and "A" to "D". Resistance should be infinite. If resistance is not as specified, replace IAC valve. (Scheme 5)

Scheme 5

Ignition Control Circuit

An open or short to ground in Ignition Control (IC) or by-pass circuit will cause PCM to turn on Malfunction Indicator Light (MIL) and confirm fault by setting a related trouble code. Refer to SELF-DIAGNOSTICS.

Knock Sensor (KS) Circuit

1. Knock sensor is mounted in engine block near cylinders. KS produces an AC output voltage which increases with severity of knock. KS sends a signal voltage to PCM. PCM will retard EST based on signal from KS to PCM. An open or short circuit on ESC wire to PCM will cause a loss of 12-volt ESC controller signal. This will cause PCM to fully retard ignition timing.
2. Disconnect connector at KS. Connect DVOM to ground, measure resistance at KS. Resistance should be 90,000-110,000 ohms. If resistance is not within specifications, If repair was not needed, replace KS. If resistance is within specifications, check KS circuit. See appropriate KNOCK SENSOR CIRCUIT DTC under SELF-DIAGNOSTICS.

EGR Valve

1. Check that EGR is securely mounted to engine. Repair as necessary. Go to next step.
2. With engine at normal operating temperature. Place transmission in park or neutral. Using a scan tool command EGR ON 50%. If engine stumbles, stalls, runs rough and looses RPMs, EGR is operating normally. If none of these conditions were found during EGR ON 50%, go to next step.
3. Turn engine off. Turn ignition on. Using a test light, check EGR ignition feed of EGR connector. If test light illuminates, go to next step. If test light does not illuminate, repair EGR harness ignition feed.
4. Remove EGR valve. Visually and physically inspect EGR valve pintle, passages through EGR and port going to EGR valve for excessive build up of carbon or other deposits. Clean, repair or replace as necessary. If EGR valve is in good condition, go to next step.
5. Ground EGR valve to battery negative terminal. Using scan tool command EGR ON and observe EGR valve pintle for movement. If movement is not seen, go to Diagnostic Trouble Code chart DTC P1406. If EGR valve movement is observed while EGR command is given, go to next step.
6. Remove EGR inlet and outlet pipes from intake and exhaust manifolds. Visually inspect manifold ports, inlet and outlet pipes for blockage or restriction caused by excessive deposits or other damage. Clean, replace or repair any or all affected components as necessary. If components are all clean and unrestricted, EGR system is operating as designed.

EGR Valve Check

With engine off, disconnect vacuum hose to EGR valve. Connect vacuum pump to EGR and apply 10 in. Hg. EGR diaphragm should move up and stay up for at least 20 seconds. If not, replace EGR valve.

EVAP Control System

A problem in the EVAP control system will set a DTC. See related DTC(s) under SELF-DIAGNOSTICS.

Required Service

The PCV system may require service for obstructions if any of the following conditions exist

1. Rough Idle
2. Stalling or Slow Idle Speed
3. Oil Leaks
4. Oil in Air Cleaner
5. Sludge in Engine A leaking PCV valve or hose could cause
6. Rough Idle
7. Stalling
8. High Idle Speed

If engine idles roughly, check for clogged PCV valve and for plugged or broken PCV hoses BEFORE adjusting idle. Check correct PCV valve application to ensure the correct valve is fitted. Replace PCV valve if required.

Checking PCV Valve Function

1. Remove PCV valve from rocker cover. Run engine at idle. Place thumb over open end of valve to check for vacuum. If there is no vacuum at valve, check for obstruction in manifold port, hoses or PCV valve. Repair or replace as necessary.
2. Turn engine off. Remove PCV valve. Shake valve and listen for rattle of check valve inside PCV valve. If a clear rattle is not heard, replace PCV valve.
3. Visually inspect valve for varnish or deposits that may make PCV valve sticky, restricted or incompletely seated. Replace if necessary.
4. Engine must be sealed for PCV system to function as designed. If leakage, sludging or dilution of oil is noted and PCV system is functioning properly, check engine for cause and repair as required to ensure PCV system will continue to function properly.
5. Since an engine operating without any crankcase ventilation can be damaged, it is important to replace PCV valve and air cleaner breather at regular intervals (at least every 30,000 miles). Check all hoses and clamps for failure or deterioration.

Brake Light Switch

1. Disconnect brake light switch harness connector. Using an ohmmeter, check continuity between brake light switch terminals No. 1 and 2. See WIRING DIAGRAMS for terminal identification. Continuity should not be present. Depress brake pedal or activate brake light switch, continuity should be present. Replace switch if not as specified.
2. Check for battery voltage at brake light switch connector. If battery voltage is not present, check 20A Stop-Hazard fuse in fuse box. If fuse is okay, check battery feed wire for an open or short. Repair as necessary.

Brake Light Switch with Cruise Control

Test brake light circuit. SEE BRAKE LIGHT SWITCH. Using an ohmmeter, check for continuity between terminals No. 3 and 4. Continuity should exist. Depress brake pedal, to deactivate cruise control. Continuity should not exist. Replace switch if not as specified.

Malfunction Indicator Light Diagnosis (MIL) No Light

See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in BASIC TESTING article.

A/C ON Switch/System Test

1. Turn ignition switch to RUN position. Move mode selector switch to any position other than OFF position. With A/C control assembly connected, measure voltage between mode selector switch and ground. For wiring schematics, see appropriate WIRING DIAGRAMS article.
2. Battery voltage should be present. If battery voltage is present, mode selector switch is operating normally. If battery voltage is not present, check wire from mode selector switch to fuse for an open circuit. Also check A/C high and low pressure switches for an open.
3. Check voltage between mode selector switch wire and ground. Voltage should not be present. If voltage is present, replace mode selector switch.

A/C Clutch Relay

1. Disconnect A/C clutch relay harness connector. Using proper mini-schematic and an ohmmeter, check continuity between A/C clutch relay winding terminals. See WIRING DIAGRAMS article. Continuity should exist. Check continuity between clutch drive circuit terminals of relay. Continuity should not exist.
2. Using jumper wires, apply ground and battery voltage to relay winding. Continuity should now exist between clutch drive circuit terminals of relay. Replace A/C clutch relay if continuity does not exist.

A/C COMPRESSOR CLUTCH RELAY LOCATION

Compressor Clutch Control Circuit Diagnosis

See appropriate AIR CONDITIONING & HEATING section for diagnosis.

Scheme 6

See also:
• G - TESTS W/CODES