Engine Controls - Basic Testing - 4-cyl 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 this 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 1) See «ENGINE CHECK CONNECTOR LOCATION»(/toyota/4runner/ii-1987-1995/remont/testing-diagnostics/#engine-controls-basic-testing-4-cyl) 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»(/toyota/4runner/ii-1987-1995/remont/testing-diagnostics/#engine-controls-basic-testing-4-cyl__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 this section in this section. 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»(/toyota/4runner/ii-1987-1995/remont/testing-diagnostics/#engine-controls-basic-testing-4-cyl). For more information on wiring, see appropriate wiring diagram in WIRING DIAGRAMS article in this section.

ENGINE CHECK CONNECTOR LOCATION

Scheme 1

FUEL SYSTEM PRESSURE TEST

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

Scheme 2

Scheme 3

1. Ensure battery is fully charged. Turn ignition off. Disconnect negative battery cable. On Previa, remove right (engine) service hole cover. On all models, place container or shop towel under fuel delivery pipe.
2. Slowly loosen delivery pipe union bolt to relieve fuel pressure. Remove union bolt and 2 gaskets. Install fuel pressure gauge between fuel supply line and delivery pipe. (Scheme 2)or (Scheme 3). Wipe off excess fuel.
3. Install jumper wire between engine check connector FP and +B pins. (Scheme 1) See «ENGINE CHECK CONNECTOR LOCATION»(/toyota/4runner/ii-1987-1995/remont/testing-diagnostics/#engine-controls-basic-testing-4-cyl) table. Connect negative battery cable. Turn ignition on, with engine off. Measure fuel pressure.
4. Fuel pressure should be same as unregulated pressure. See «FUEL PUMP PERFORMANCE»(/toyota/4runner/ii-1987-1995/remont/testing-diagnostics/#engine-controls-basic-testing-4-cyl) table. 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.
5. 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. Measure unregulated fuel pressure at idle speed. See «FUEL PUMP PERFORMANCE»(/toyota/4runner/ii-1987-1995/remont/testing-diagnostics/#engine-controls-basic-testing-4-cyl) table.
6. With engine idling, connect fuel pressure regulator vacuum hose. Measure regulated pressure at idle. If regulated pressure is not as specified, check vacuum sensing hose to fuel pressure regulator.
7. 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 ). If pressure is not as specified, check for leaking injectors, faulty fuel pressure regulator or bad check valve in fuel pump.
8. Relieve fuel system pressure. Remove fuel pressure gauge. Install fuel supply line to delivery pipe. Run engine and check for fuel leaks.

Scheme 4

Scheme 5

Scheme 6

Scheme 7

Scheme 8

1. Ensure battery is fully charged. Turn ignition off. Disconnect negative battery cable. On Tercel, place container or shop towel under fuel filter.
2. On all other models, 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. Remove union bolt and gaskets. Install fuel pressure gauge to cold start injector delivery pipe. see scheme 4-9. Wipe off excess fuel.
4. Install jumper wire between engine check connector FP and +B pins. (Scheme 1) See «ENGINE CHECK CONNECTOR LOCATION»(/toyota/4runner/ii-1987-1995/remont/testing-diagnostics/#engine-controls-basic-testing-4-cyl) table. Reconnect negative battery cable, and turn ignition on, with engine off. Measure fuel pressure. Fuel pressure should be same as unregulated pressure. See «FUEL PUMP PERFORMANCE»(/toyota/4runner/ii-1987-1995/remont/testing-diagnostics/#engine-controls-basic-testing-4-cyl) 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 the «FUEL PUMP PERFORMANCE»(/toyota/4runner/ii-1987-1995/remont/testing-diagnostics/#engine-controls-basic-testing-4-cyl) 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 this 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 9) 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 this section in this section.

Scheme 9

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. On all models except Celica, Corolla (4A-FE) and Tercel, fuel pump switch in airflow meter provides relay ground. On Celica, Corolla (4A-FE) and Tercel, circuit opening relay is grounded by ECU through FC terminal.

Fuel Pump Relay & Fuel Pump Resistor (Celica 2.0L Turbo)

These models use a separate fuel pump relay and resistor between circuit opening relay and fuel pump.

Note. For more information on testing relays and fuel system components, see I - SYS/COMP TESTS article in this 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 this 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. Refer to the 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»(/toyota/4runner/ii-1987-1995/remont/testing-diagnostics/#engine-controls-basic-testing-4-cyl) 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»(/toyota/4runner/ii-1987-1995/remont/testing-diagnostics/#engine-controls-basic-testing-4-cyl) . 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»(/toyota/4runner/ii-1987-1995/remont/testing-diagnostics/#engine-controls-basic-testing-4-cyl) . 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»(/toyota/4runner/ii-1987-1995/remont/testing-diagnostics/#engine-controls-basic-testing-4-cyl__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 this 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 10)-24.
2. If primary resistance is not within specification, replace ignition coil. See appropriate «IGNITION COIL RESISTANCE»(/toyota/4runner/ii-1987-1995/remont/testing-diagnostics/#engine-controls-basic-testing-4-cyl) table. If resistance is within specification, proceed to SECONDARY COIL RESISTANCE TEST below.

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. See «IGNITION COIL RESISTANCE»(/toyota/4runner/ii-1987-1995/remont/testing-diagnostics/#engine-controls-basic-testing-4-cyl) table. (Scheme 10)-24.
2. If resistance is not within specification, replace ignition coil. If resistance is within specification, proceed to «PICK-UP COIL RESISTANCE TEST»(/toyota/4runner/ii-1987-1995/remont/testing-diagnostics/#engine-controls-basic-testing-4-cyl).

IGNITION COIL RESISTANCE (1)

Scheme 10

Scheme 11

Scheme 12

Scheme 13

Scheme 14

Scheme 15

Camry (2.0L) & Tercel

1. Measure pick-up coil resistance between terminals "G" and G(-) and between terminals NE and G(-). (Scheme 16)
2. If resistance is not within specification, replace distributor. See «DISTRIBUTOR PICK-UP COIL RESISTANCE»(/toyota/4runner/ii-1987-1995/remont/testing-diagnostics/#engine-controls-basic-testing-4-cyl) table. If resistance is within specification, proceed to «PICK-UP COIL AIR GAP CHECK»(/toyota/4runner/ii-1987-1995/remont/testing-diagnostics/#engine-controls-basic-testing-4-cyl__pick-up-coil-air-gap-check).

Pick-up Coil Connector ID (Camry & Tercel) Toyota Motor Sales, U.S.A., Inc. Scheme 16

Celica (1.6L) & Corolla (4A-FE)

1. Measure pick-up coil resistance between terminals G(+) and G(-) and between terminals NE(+) and G(-). (Scheme 17)
2. If resistance is not within specification, replace distributor. See «DISTRIBUTOR PICK-UP COIL RESISTANCE»(/toyota/4runner/ii-1987-1995/remont/testing-diagnostics/#engine-controls-basic-testing-4-cyl) table. If resistance is within specification, proceed to «PICK-UP COIL AIR GAP CHECK»(/toyota/4runner/ii-1987-1995/remont/testing-diagnostics/#engine-controls-basic-testing-4-cyl__pick-up-coil-air-gap-check).

Pick-up Coil Connector ID (Celica 1.6 & Corolla 4A-FE) Toyota Motor Sales, U.S.A., Inc. Scheme 17

Celica (2.0L), MR2 (2.0L) & Previa

1. Measure resistance of pick-up coil between terminals G1 and G(-), G2 and G(-) and NE and G(-). (Scheme 18)
2. If resistance is not within specification, replace distributor. See «DISTRIBUTOR PICK-UP COIL RESISTANCE»(/toyota/4runner/ii-1987-1995/remont/testing-diagnostics/#engine-controls-basic-testing-4-cyl) table. If resistance is within specification, proceed to «PICK-UP COIL AIR GAP CHECK»(/toyota/4runner/ii-1987-1995/remont/testing-diagnostics/#engine-controls-basic-testing-4-cyl__pick-up-coil-air-gap-check).

Pick-up Coil Connector ID (Celica 2.0L, MR2 2.0L & Previa) Toyota Motor Sales, U.S.A., Inc. Scheme 18

Celica (2.2L) & MR2 (2.2L)

1. Measure pick-up coil resistance between terminals G1 and G(-) and between NE and G(-). (Scheme 19)
2. If resistance is not within specification, replace distributor. See «DISTRIBUTOR PICK-UP COIL RESISTANCE»(/toyota/4runner/ii-1987-1995/remont/testing-diagnostics/#engine-controls-basic-testing-4-cyl) table. If resistance is within specification, proceed to «PICK-UP COIL AIR GAP CHECK»(/toyota/4runner/ii-1987-1995/remont/testing-diagnostics/#engine-controls-basic-testing-4-cyl__pick-up-coil-air-gap-check).

Pick-up Coil Connector ID (Celica 2.2L & MR2 2.2L) Toyota Motor Sales, U.S.A., Inc. Scheme 19

Corolla (4A-GE)

1. Measure pick-up coil resistance between terminals G(+) and G(-) and between NE(+) and NE(-). (Scheme 20)
2. If resistance is not within specification, replace distributor. See «DISTRIBUTOR PICK-UP COIL RESISTANCE»(/toyota/4runner/ii-1987-1995/remont/testing-diagnostics/#engine-controls-basic-testing-4-cyl) table. If resistance is within specification, proceed to «PICK-UP COIL AIR GAP CHECK»(/toyota/4runner/ii-1987-1995/remont/testing-diagnostics/#engine-controls-basic-testing-4-cyl__pick-up-coil-air-gap-check).

Pick-up Coil Connector ID (Corolla 4A-GE) Toyota Motor Sales, U.S.A., Inc. Scheme 20

Pickup (2.4L) & 4Runner (2.4L)

1. Measure resistance of pick-up coil between terminals NE (+) and NE (-). (Scheme 21)
2. If resistance is not within specification, replace distributor. See «DISTRIBUTOR PICK-UP COIL RESISTANCE»(/toyota/4runner/ii-1987-1995/remont/testing-diagnostics/#engine-controls-basic-testing-4-cyl) table. If resistance is within specification, proceed to «PICK-UP COIL AIR GAP CHECK»(/toyota/4runner/ii-1987-1995/remont/testing-diagnostics/#engine-controls-basic-testing-4-cyl__pick-up-coil-air-gap-check).

Pick-up Coil Connector ID (Pickup & 4Runner) Toyota Motor Sales, U.S.A., Inc. Scheme 21

DISTRIBUTOR PICK-UP COIL RESISTANCE

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 22)-37.
2. Air gap should be within specification. See «PICK-UP COIL ADJUSTMENT»(/toyota/4runner/ii-1987-1995/remont/testing-diagnostics/#engine-controls-basic-testing-4-cyl) table. If air gap is not within specification, replace distributor.

PICK-UP COIL ADJUSTMENT

Scheme 22

Scheme 23

Scheme 24

Scheme 25

Scheme 26

Scheme 27

IDLE SPEED & IGNITION TIMING

Ensure idle speed and ignition timing are set to specification. For adjustment procedures, see ADJUSTMENTS article in this section.

IDLE SPEED

IDLE SPEED SPECIFICATIONS

IGNITION TIMING

IGNITION TIMING (1)

SUMMARY

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

See also:
• ENGINE CHECK CONNECTOR LOCATION
• FUEL SYSTEM PRESSURE TEST
• PICK-UP COIL AIR GAP CHECK