Ground Circuits
- Using an ohmmeter, check for continuity to ground on ECM terminals as follows: On Maxima, terminals No. 10, 19, 25, 32, 43, 108, 116 and 124. (Scheme 36) Resistance should be zero ohms. If resistance is not zero ohms, repair open to ground.
- Using a DVOM, touch negative lead of voltmeter to a good ground. Using positive lead of voltmeter, backprobe each ground terminal at ECM connector. With vehicle running, voltmeter should indicate less than one volt. If voltmeter reading is greater than one volt, check for open, corrosion or loose connection on ground lead.
Power Circuits
- Turn ignition switch to ON position. Using a voltmeter, check for battery voltage between chassis ground and ECM terminals as follows: On Maxima, terminals No. 24, 67 and 72. (Scheme 36) If battery voltage is not present, check fusible link and fuse "G".
- Turn ignition switch to OFF position. Using a voltmeter, check for battery voltage between chassis ground and ECM power back-up terminals as follows: On Maxima, terminal No. 80. If battery voltage is not present, check for overheated relays, fusible links and wiring.
Scheme 36
ENGINE SENSORS & SWITCHES
Note. For ECM connector terminal identification, see PIN VOLTAGE CHART S article and WIRING DIAGRAMS article.
CAMSHAFT POSITION SENSOR
Faults in camshaft position sensor circuit should set Diagnostic Trouble Code (DTC) PO340. To test system, see DTC P0340: CAMSHAFT POSITION (CMP) SENSOR procedures in appropriate G - TESTS W/CODES article.
CLOSED THROTTLE POSITION SWITCH
Faults in closed throttle position switch or circuit should set Diagnostic Trouble Code (DTC) PO510. To test system, see DTC P0510: CLOSED THROTTLE POSITION SWITCH procedures in appropriate TESTS W/CODES article.
INHIBITOR SWITCH
Faults in the inhibitor switch should set Diagnostic Trouble Code (DTC) PO705. For testing procedure, refer to DTC P0705: PARK/NEUTRAL POSITION SWITCH procedures in appropriate TESTS W/CODES article.
KNOCK SENSOR
Faults in knock sensor or circuit should set a Diagnostic Trouble Code (DTC) P0325. For testing procedure, refer to DTC P0325: KNOCK SENSOR (KS) in appropriate TESTS W/CODES article. To locate sensor, see DETONATION SENSOR LOCATION table.
| Application | Location |
|---|---|
| Maxima | On Intake Side Of Cylinder Block |
KNOCK SENSOR LOCATION
ENGINE COOLANT TEMPERATURE (ECT) SENSOR
Faults in engine (coolant) temperature sensor circuit should set Diagnostic Trouble Code (DTC) P0115, or DTC P0125. To test system, see DTC P0115 OR P0125: ENGINE COOLANT TEMPERATURE (ECT) SENSOR in appropriate TESTS W/CODES article.
| Application | Location |
|---|---|
| Maxima | On Intake Manifold, At Flywheel-End Of Left Cylinder Head |
ENGINE COOLANT TEMPERATURE (ECT) SENSOR LOCATION
| Temperature °F (°C) | Ohms |
|---|---|
| 68 (20) | 2100-2900 |
| 122 (50) | 680-1000 |
| 176 (80) | 300-330 |
| 194 (90) | 236-260 |
ENGINE (COOLANT) TEMPERATURE SENSOR RESISTANCE
EGR TEMPERATURE SENSOR
Faults in exhaust gas temperature sensor circuit should set DTC P1401. To test system, see DTC P1401: EGR TEMPERATURE SENSOR diagnostic procedures in appropriate TESTS W/CODES article.
FUEL TEMPERATURE SENSOR
Faults in fuel temperature sensor or circuit should set DTC P0180. To test system, see DTC P0180: TANK FUEL TEMPERATURE (TFT) SENSOR.
INTAKE AIR TEMPERATURE (IAT) SENSOR
Faults in IAT sensor or circuit should set a Diagnostic Trouble Code (DTC) PO110. For testing procedure, refer to DTC P0110: INTAKE AIR TEMPERATURE (IAT) SENSOR in appropriate TESTS W/CODES article.
HEATED OXYGEN SENSOR (HO2S)
Faults in oxygen sensor circuit may set DTC P0150/P0155 (left front), DTC P0130/P0135 (right front), or DTC P0136 (rear). To test system, see diagnostic procedures in appropriate TESTS W/CODES article.
MASS AIRFLOW SENSOR
Faults in mass airflow sensor circuit should set Diagnostic Trouble Code (DTC) P0100. For testing procedure, refer to DTC P0100: MASS AIRFLOW (MAF) SENSOR in appropriate TESTS W/CODES article.
NEUTRAL POSITION SWITCH
Faults in vehicle speed sensor circuit should DTC P0500. To test system, see DTC P0705: PARK/NEUTRAL POSITION SWITCH diagnostic procedures in appropriate TESTS W/CODES article.
POWER STEERING OIL PRESSURE SWITCH
- Disconnect power steering oil pressure switch connector. Switch is attached to power steering high pressure hose. Replace switch if resistance is not 2-3 ohms.
- On all other models, start engine and check switch for continuity. Replace switch if continuity is not as specified in POWER STEERING OIL PRESSURE SWITCH.
| Condition | Continuity |
|---|---|
| Steering Unloaded (Not Turning Steering Wheel) | No |
| Steering Loaded (Turning Steering Wheel) | Yes |
POWER STEERING OIL PRESSURE SWITCH
THROTTLE POSITION (TP) SENSOR
Faults in TP sensor circuit should set DTC P0120. To test system, see DTC P0120: THROTTLE POSITION (TP) SENSOR diagnostic procedures in appropriate TESTS W/CODES article.
VEHICLE SPEED SENSOR
Faults in vehicle speed sensor circuit should DTC P0500. To test system, see DTC P0500: VEHICLE SPEED SENSOR (VSS) diagnostic procedures in appropriate TESTS W/CODES article.
RELAYS
The following relays can be tested using an ohmmeter and remotely supplied power and ground circuits
- Electronic Control Module (ECM or ECCS) relay.
- Fuel pump relay.
- Radiator (cooling) fan relay.
- Park/neutral position (inhibitor) relay.
ECCS & Fuel Pump Relays
- Two types of relays are used; 4-terminal and 6-terminal. For relay location, see RELAY LOCATION & IDENTIFICATION table. On all relays, apply battery voltage and ground to terminals No. 1 and 2. (Scheme 37)or (Scheme 38).
- On 4-terminal relays, continuity should exist between terminals No. 3 and 5. On 6-terminal relays, continuity should exist between terminals No. 3, 5, 6 and 7. When battery voltage is removed, continuity should not exist. Replace relay if test values are not as specified.
Park/Neutral Position (Inhibitor) Relay
For testing procedure, refer to DTC P0705: PARK/NEUTRAL POSITION SWITCH procedures in appropriate TESTS W/CODES article. Radiator (Cooling) Fan Relay
For testing procedure, refer to DTC P1900: RADIATOR (COOLING) FAN CONTROL procedures in appropriate TESTS W/CODES article.
Scheme 37
Scheme 38
EGR Control (ECCS) Solenoid
See EXHAUST GAS RECIRCULATION (EGR) under EMISSION SYSTEMS & SUB-SYSTEMS.
EGR & Canister Control Solenoid
See EXHAUST GAS RECIRCULATION (EGR) under EMISSION SYSTEMS & SUB-SYSTEMS.
Fast Idle Control Device (FICD) Solenoid
See FAST IDLE CONTROL DEVICE (FICD) SOLENOID under IDLE CONTROL SYSTEMS.
FUEL DELIVERY
Note. For fuel system pressure testing, see FUEL PRESSURE under FUEL SYSTEM in BASIC TESTING article. If ECM receives incorrect start (cranking) signal, fuel delivery system may not operate properly. See START SIGNAL under IGNITION SYSTEMS.
Fuel Pressure Regulator
Connect fuel pressure gauge. Disconnect vacuum hose from fuel pressure regulator. Plug hose end. Connect hand-held vacuum pump to fuel pressure regulator. Start engine. Gradually apply vacuum to fuel pressure regulator. Compare fuel pressure to regulated pressure in FUEL PRESSURE table in BASIC TESTING article. If pressure is not as specified, replace fuel pressure regulator.
FUEL PUMP
To test fuel pump, disconnect fuel pump connector, accessible through trunk. At fuel pump connector, check resistance between fuel pump terminals specified in FUEL PUMP RESISTANCE TEST table. If resistance is not as specified, replace fuel pump.
| Application | Terminals (Wire Colors) | Ohms |
|---|---|---|
| Maxima | Black/Yellow & Green/Red | 0.2-5.0 |
FUEL PUMP RESISTANCE TEST
FUEL PUMP CONTROL MODULE & DROPPING RESISTOR
Faults in fuel pump control module & dropping resistor circuit should set Diagnostic Trouble Code (DTC) P1220. To test system, see DTC P1220: FUEL PUMP CONTROL MODULE (FPCM) procedures in appropriate TESTS W/CODES article.
FUEL INJECTOR
Disconnect fuel injector harness connector. Check resistance across injector connector terminals. If resistance is not as specified in INJECTOR RESISTANCE SPECIFICATIONS table, replace injector. If resistance is okay, remove injector. If nozzle is clogged, replace injector.
| Application | Ohms |
|---|---|
| Maxima | 10-14 |
INJECTOR RESISTANCE SPECIFICATIONS
IDLE AIR CONTROL (IAC) VALVE
Faults in IAC valve or circuit should set Diagnostic Trouble Code (DTC) PO505. To test system, see procedures in DTC P0505: IDLE AIR CONTROL (IAC) in appropriate TESTS W/CODES .
Disconnect FICD solenoid harness connector. Apply battery voltage across solenoid terminals. If solenoid does not operate, check for sticking plunger or broken spring. If plunger and spring are okay, replace solenoid.
IGNITION SYSTEMS
Faults in ignition signal should set a DTC P1320. For testing procedure, refer to DTC P1320: IGNITION SIGNAL in appropriate TESTS W/CODES article.
POWER TRANSISTOR
Faults in power transistor should set a DTC P1320. For testing procedure, refer to DTC P1320: IGNITION SIGNAL in appropriate TESTS W/CODES article.
Timing Advance
Ignition timing advance is controlled by the ECM based upon sensor input signals. If timing problems are experienced, inspect input signals for proper operation. See PIN VOLTAGE CHART S article. Inputs that affect timing include the following
- Camshaft or crankshaft position sensor.
- Airflow meter.
- Engine (coolant) temperature sensor.
- Idle switch.
- Start (cranking) signal.
- Battery voltage.
Detonation (Knock) Retard
Check knock sensor wire for open or short to ground. Check knock sensor shield ground wire for continuity to ground. Check routing of knock sensor wire. Wire should not be routed close to spark plug wires or high output accessories.
Faults in knock sensor (detonation retard) circuit may set Code 34 or DTC P0325. To test system, refer to DTC PO340: CAMSHAFT POSITION (CMP) SENSOR in appropriate TESTS W/CODES article.
Carbon Canister
Remove hoses from carbon canister. Blow air into canister ports as shown. (Scheme 39) Air should pass through vent and purge lines, but should not pass through vacuum lines.
Fuel Tank Vacuum Relief Valve
Valve is located in fuel tank filler cap. Wipe cap clean to prevent inhaling fuel vapors. Find a way to safely apply light vacuum to cap on side of cap that faces fuel tank. A slight resistance accompanied by clicks indicates the valve is okay. By applying more vacuum, resistance should no longer be felt and clicks should no longer be heard. If valve does not operate as specified, replace fuel tank filler cap.
Fuel Vapor Check Valve
Disconnect hoses from fuel vapor check valve. Apply light air pressure to fitting on side of valve that leads to fuel tank. Resistance should be felt, but some air should flow out of fitting that leads to carbon canister. Apply light air pressure to fitting that leads to carbon canister. Air should flow freely through valve. If valve does not operate as described, replace valve.
Scheme 39
EGR Backpressure Transducer (EGR-BPT)
Plug one port of EGR-BPT valve and apply vacuum to other port. Vacuum should NOT hold. Apply light pressure to bottom port (DO NOT apply more pressure than is necessary to cause vacuum to hold). If vacuum does not hold with pressure applied, replace EGR-BPT.
EGR Control (EGRC) Solenoid
Faults in EGRC solenoid circuit should set DTC P0400. To test circuit, see DTC P0400 diagnostic procedures in appropriate TESTS W/CODES article.
Faults in EGR and canister control solenoid circuit should set DTC P1400. To test circuit, see DTC P1400 diagnostic procedures in appropriate TESTS W/CODES article.
EGR Function
Faults in EGR function circuit should set DTC P0400. To test function, DTC P0400 diagnostic procedures in appropriate TESTS W/CODES article.
EGR Valve
- With engine idling, disconnect EGR vacuum line. Apply vacuum to EGR valve. Engine speed should decrease or engine should stall. If engine does not respond in this manner, go to next step. Vacuum should hold on gauge. If vacuum does not hold, replace EGR valve.
- Manually compress EGR valve diaphragm from underside. If engine speed does not decrease or engine does not stall, remove EGR valve and inspect EGR passages for plugging. If engine speed decreases or engine stalls, replace EGR valve.
POSITIVE CRANKCASE VENTILATION (PCV)
With engine idling, disconnect ventilation hose from PCV valve. If a hissing noise and strong vacuum are not present at hose end, check hose and hose connections for leaks or obstructions. Repair or replace as necessary.
MISCELLANEOUS CONTROLS
Note. Although some of the controlled devices listed here are not technically engine performance components, they can affect driveability if they malfunction.
ELECTRICAL LOAD
- Turn ignition off. Disconnect ECM harness connector. ECM is located under center of instrument panel (connector is located on passenger's side). Turn ignition on. Measure voltage between ground and ECM terminal No. 79 (Red/White wire).
- With rear window defogger or headlights on (2nd position), battery voltage should exist. With rear window defogger or headlights off, zero volts should exist. If voltage is not as specified, go to next step. If voltage is as specified, system is functioning properly.
- Turn ignition off. Disconnect rear window defogger relay. Measure voltage between ground and rear window defogger relay terminal No. 3 (Blue wire). If battery voltage exists, go to next step. If voltage does not exist, check 20-amp fuse, harness, and connectors between battery and relay.
- Check continuity between ECM terminal No. 79 (Red/White wire) and rear window defogger relay terminal No. 5 (Blue/Red wire). Continuity should exist. If continuity exists, go to next step. If continuity does not exist, check harness and connectors between ECM and relay.
- Turn ignition off. Disconnect lighting switch harness connector. Check continuity between ECM terminal No. 79 (Red/White wire) and lighting switch harness connector terminal No. 12 (Red/Green wire; terminal No. 9 and Yellow wire on California models). Continuity should exist. If continuity exists, system is functioning properly. If continuity does not exist, check 7.5-amp fuse or diode (if equipped), harness, and connectors between ECM and lighting switch.
RADIATOR COOLING FANS
The ECM controls electric radiator cooling fan(s) based on vehicle speed, engine coolant temperature and A/C switch position. A fault in radiator fan control circuit should set DTC P1900. To test system, see diagnostic procedures in DTC P1900: RADIATOR COOLING FAN CONTROL in appropriate TESTS W/CODES article.