Engine Controls - Basic Testing - v6 Toyota 4Runner II

INTRODUCTION

The following diagnostic steps will help prevent overlooking a simple problem. This is also where to begin diagnosis for a no-start condition.

The first step in diagnosing any driveability problem is verifying the customer's complaint with a test drive under the conditions the problem reportedly occurred.

Before entering self-diagnostics, perform a careful and complete visual inspection. Most engine control problems result from mechanical breakdowns, poor electrical connections or damaged/misrouted vacuum hoses. Before condemning the computerized system, perform each test listed in this article.

Note. Perform all voltage tests with a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure.

VISUAL INSPECTION

Visually inspect all electrical wiring, looking for chafed, stretched, cut or pinched wiring. Ensure electrical connectors fit tightly and are not corroded. Ensure vacuum hoses are properly routed and are not pinched or cut. See VACUUM DIAGRAMS article in the ENGINE PERFORMANCE Section to verify routing and connections (if necessary). Inspect air induction system for possible vacuum leaks.

Compression

Check engine mechanical condition with a compression gauge, vacuum gauge, or an engine analyzer. See engine analyzer manual for specific instructions.

COMPRESSION SPECIFICATIONS

Exhaust System Backpressure

The exhaust system can be checked with a vacuum or pressure gauge. Remove O2 sensor or air injection check valve (if equipped). Connect a 1-10 psi pressure gauge and run engine at 2500 RPM. If exhaust system backpressure is greater than 2 psi, exhaust system or catalytic converter is plugged.

If a vacuum gauge is used, connect vacuum gauge hose to intake manifold vacuum port and start engine. Observe vacuum gauge. Open throttle part way and hold steady. If vacuum gauge reading slowly drops after stabilizing, exhaust system should be checked for a restriction.

FUEL SYSTEM

Basic diagnosis of fuel system should begin with determining fuel system operation and pressure.

Fuel Pressure Release

Disconnect negative battery terminal. Place container under fitting to be loosened. Use a rag to cover fuel line/component. Slowly loosen fitting, allowing pressurized fuel to spill into container. After fuel system has depressurized, disconnect and plug fitting.

FUEL PUMP QUICK TEST

1. Turn ignition on, with engine off. Place jumper wire across +B and FP terminals of engine check connector in engine compartment. (Scheme 28) See ENGINE CHECK CONNECTOR LOCATION table.
2. Listen for fuel pump running sound. Feel for pressure in fuel line between filter and fuel rail. Turn ignition off. Remove jumper wire. If fuel pump sound was present and fuel hose showed pressure, go to FUEL SYSTEM PRESSURE TEST.
3. If no pressure or fuel pump sound was present, connect a jumper wire from battery source to FP terminal of engine check connector.
4. If fuel pump does not run or no fuel pressure is felt in line, check for defective fuel pump. Check for open circuit between engine check connector and fuel pump or for poor fuel pump ground. See appropriate wiring diagram in WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section in ENGINE PERFORMANCE. NOTE: All models use in-tank fuel pump. Fuel pump contains internal relief valve and check valve.
5. If fuel pump ran after battery source was connected to FP terminal in step 3), check EFI main relay and related wiring. Also check EFI and IGN fuses. See FUEL PUMP CONTROL CIRCUIT. For more information on wiring, see appropriate wiring diagram in WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

ENGINE CHECK CONNECTOR LOCATION

Scheme 28

FUEL SYSTEM PRESSURE TEST

Note. Before testing fuel pressure, check all fuel delivery and return lines for leaks.

Scheme 29

Scheme 30

1. Ensure battery is fully charged. Turn ignition off. Disconnect negative battery cable. On Pickup and 4Runner, place container or shop towel under No. 3 fuel supply pipe.
2. On Camry, place container or shop towel under cold start injector. Disconnect cold start injector (if equipped). Slowly loosen cold start injector or No. 3 fuel supply pipe union bolt to relieve fuel pressure.
3. On Camry remove union bolt and gaskets. Install fuel pressure gauge to cold start injector delivery pipe. (Scheme 29)and (Scheme 30). Wipe off excess fuel. On Pickup and 4Runner, attach gauge to No. 3 fuel pipe using same method. (Scheme 29)and (Scheme 30).
4. Install jumper wire between engine check connector FP and +B pins. (Scheme 28) See ENGINE CHECK CONNECTOR LOCATION table. Reconnect negative battery cable, and turn ignition on, with engine off. Measure fuel pressure. Fuel pressure should be same as unregulated pressure. See appropriate FUEL PUMP PERFORMANCE table.
5. If fuel pressure is high, replace fuel pressure regulator. If fuel pressure is low, check fuel hoses and connections, fuel pump, fuel filter, and fuel pressure regulator
6. Remove jumper wire installed in step 3). Start engine. Disconnect vacuum sensing hose from fuel pressure regulator, and plug hose end. Fuel pressure regulator is mounted on fuel rail.
7. Measure unregulated fuel pressure at idle speed. See appropriate FUEL PUMP PERFORMANCE table. With engine still idling, reconnect fuel pressure regulator vacuum hose.
8. Measure regulated pressure at idle. If regulated pressure is not as specified, check vacuum sensing hose to fuel pressure regulator. On models so equipped, check fuel pressure-up system. See & I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.
9. Stop engine. Note fuel pressure. Leave fuel pressure gauge attached to engine for at least 5 minutes. Residual fuel pressure after 5 minutes should be at least 21 psi (1.5 kg/cm 2 ).
10. If pressure is not as specified, check for leaking injectors, faulty fuel pressure regulator or bad check valve in fuel pump. Relieve fuel system pressure. Remove fuel pressure gauge. Install cold start injector. Run engine and check for fuel leaks.

Note. For more information on checking fuel injectors and other fuel sub-systems, see I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.

FUEL PUMP PERFORMANCE

EFI Main Relay

1. EFI fuse supplies constant battery voltage to EFI main relay. EFI main relay provides battery voltage to +B terminal of circuit opening relay and engine check connector.
2. If fuel pump does not turn on when +B and FP pins are jumpered with ignition on, check EFI main relay. (Scheme 31) Also check EFI main relay circuit. Depending on model, relay may either be turned on directly by ignition switch or by M-REL terminal of ECU. For more information on wiring, see WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section in ENGINE PERFORMANCE.

Scheme 31

Circuit Opening Relay

1. Circuit opening relay controls fuel pump circuit. ECU receives an input signal at STA terminal when engine is cranking. This starter signal is also applied to terminal STA of circuit opening relay.
2. Starter signal energizes circuit opening relay during cranking, which in turn activates fuel pump. Fuel pump switch in airflow meter provides relay ground.

Note. For more information on testing relays and fuel system components, see I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.

DIAGNOSTIC CODES

Note. ECU is programmed to detect ignition problems. Checking for trouble codes can speed up diagnosis. If ECU detects a problem, a diagnostic code will be set in memory. For information on system self-diagnostic capabilities and how to retrieve codes, see TESTS W/CODES article in the ENGINE PERFORMANCE Section.

Code 12 (No RPM Signal)

ECU will store Code 12 in memory if it does not receive signal from either NE pick-up coil (RPM) or "G" pick-up coil (crank position) terminal within 2 seconds of engine cranking.

Code 13 (No RPM Signal)

ECU will store Code 13 in memory if it does not receive signal from NE pick-up coil (RPM) terminal when engine speed is above 1000 RPM.

Code 14 (Ignition Signal Problem)

ECU will store Code 14 in memory if it does not receive IGF (ignition detection) signal a specified number of times. See CODE 14 SET SPECIFICATIONS table.

CODE 14 SET SPECIFICATIONS

SPARK TEST

1. On models with integral ignition coil, disconnect spark plug wires. Remove spark plugs. Install spark plugs to each spark plug wire. Ground spark plug.
2. On models with external ignition coil, disconnect high tension (coil) wire from distributor. Hold wire about 1/2" away from ground. CAUTION: To prevent gasoline from being injected, DO NOT crank engine for longer than 2 seconds.
3. On all models, crank engine and check for spark. If spark does not occur, check ignition coil, ignitor and distributor connections.
4. If connections are good, check resistance of high tension wires. See IGNITION HIGH-TENSION WIRE RESISTANCE table. If resistance is within specification, go to next step. If resistance is not within specification, replace wires.
5. Check power supply to ignition coil and ignitor. Place ignition switch in ON position. Check for voltage at ignition coil positive terminal. If voltage is present, go to next step. If voltage is not present, check wiring between ignition switch, coil and ignitor.
6. Check ignition coil resistance. See IGNITION COIL RESISTANCE TESTS. If ignition coil resistance is not as specified, replace coil. If coil resistance is within specification, go to next step.
7. Check pick-up coil resistance. See PICK-UP COIL RESISTANCE TEST. If resistance is within specification, go to next step. If pick-up coil resistance is not as specified, replace pick-up coil or distributor assembly.
8. Check air gap between reluctor and pick-up coil. See PICK-UP COIL AIR GAP CHECK. If air gap is correct, go to next step. If air gap is incorrect, replace distributor assembly.
9. Check ignition IGT signal from ECU. See appropriate CODE 14 chart in TESTS W/CODES article in the ENGINE PERFORMANCE Section. If IGT signal is okay, replace ignitor.

Note. A loss of either IGT or IGF signal will cause a no-start condition.

IGNITION HIGH-TENSION WIRE RESISTANCE

Primary Coil Resistance Test

1. Disconnect ignition coil so it is isolated from remainder of system. Using an ohmmeter, measure resistance between coil positive (+) and negative (-) terminals. (Scheme 32)and (Scheme 33). Resistance should be 0.4-0.5 ohms at 68°F (20°).
2. If primary resistance is not within specification, replace ignition coil. If resistance is within specification, proceed to SECONDARY COIL RESISTANCE TEST.

Scheme 32

Scheme 33

Secondary Coil Resistance Test

1. Disconnect ignition coil so it is isolated from remainder of system. Using an ohmmeter, measure resistance between coil positive (+) terminal and coil tower. (Scheme 34)and (Scheme 35). Resistance should be 10,200-13,800 ohms at 68°F (20°C).
2. If resistance is not within specification, replace ignition coil. If resistance is within specification, proceed to PICK-UP COIL RESISTANCE TEST.

Scheme 34

Scheme 35

PICK-UP COIL RESISTANCE TEST

1. Measure pick-up coil resistance between terminals G1 and G(-), G2 and G(-) and NE and G(-). (Scheme 36)
2. If resistance is incorrect, replace distributor. See DISTRIBUTOR PICK-UP COIL RESISTANCE table. If resistance is within specification, proceed to PICK-UP COIL AIR GAP CHECK.

DISTRIBUTOR PICK-UP COIL RESISTANCE

Scheme 36

PICK-UP COIL AIR GAP CHECK

1. Using a flat, non-magnetic feeler gauge, check air gap between signal rotor and pick-up coil projection. (Scheme 37)& 11.
2. Air gap should be within specification. See PICK-UP COIL ADJUSTMENT table. If air gap is not within specification, replace distributor.

PICK-UP COIL ADJUSTMENT

Scheme 37

Scheme 38

IDLE SPEED & IGNITION TIMING

Ensure idle speed and ignition timing are set to specification. For adjustment procedures, see ADJUSTMENTS article in the ENGINE PERFORMANCE Section.

IDLE SPEED

IDLE SPEED SPECIFICATIONS

IGNITION TIMING

IGNITION TIMING

SUMMARY

If no faults were found while performing BASIC TESTING , proceed to TESTS W/CODES article in the ENGINE PERFORMANCE Section. If no hard codes are found in self-diagnostics, proceed to TESTS W/O CODES article in the ENGINE PERFORMANCE Section for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.