Nissan offers CONSULT tests for a fee to pin point problems through the ECU. There are procedures to get some of the same results without a CONSULT tool from the ECU's memory.  1. Remove the passenger floor mat (1.).  2. Pull back carpet. It's held up with 3 spots of velcro (2.).  3. Remove the wooden floorboard (3.) (4 x 10 mm bolts)  4. The screw potentiometer is on the right side of the ECU, the coding LED is in the oval hole above it (4.).  5. Turn the ignition switch on, but do not start the engine.  6. Turn 'diagnostic mode selector' (pot on side) fully clockwise. Wait at least 2 seconds, then turn pot fully counter clock-wise. The ECU is now in Diagnostics MODE II  7. Read the codes from the flashing LED on the side of the ECU (or the check engine light). Long flash is first digit, short flash is 2nd digit, the codes are at the bottom of this page.  8. To exit MODE II, turn pot fully clock-wise. Wait at least 2 seconds, then turn the potentiometer fully counter clock-wise, or...  9. Start engine with the ECU in MODE II to enter MODE II - Heated Oxygen Sensor (O2) Monitor . The ECU is now monitoring the left O2 sensor. Warm the engine to normal operating temperature, then run at 2000 rpm for 2 minutes. Check that the LED blinks (or the check engine light) more than 5 times every 10 seconds at 2000 rpm.  10. To change to right sensor turn the ECU potentiometer clockwise with engine still running, wait 2 seconds, turn it back. Check the lights at 2000 rpm again for a similar switching condition.  NOTE: Light indicates signal from sensor to ecu. ON=rich, Off=lean. Blinking light means system is constantly adjusting between lean and rich which is normal. Any other indication would be abnormal and require further investigation. The switched on/off is 'closed loop', while a constant on or off is 'open loop' 11. To exit MODE II - Heated Oxygen Sensor Monitor, turn the potentiometer fully counter clock-wise and stop the engine.  LED codes for MODE II: 11: crank angle sensor circuit  12*: air flow meter circuit  13*: engine coolant temp. sensor circuit  14*: vehicle speed sensor circuit  21: ignition signal circuit  26*: boost pressure sensor  31*: ECU  32*: EGR function  33*: exhaust gas sensor circuit (left)  34: detonation sensor circuit  35*: exhaust gas temp. sensor circuit  42: fuel temp. sensor circuit  43*: throttle position sensor circuit  45*: injector leak  51*: injector circuit  53*: exhaust gas sensor circuit (right)  54: signal circuit from A/T control to ECU  55: NO malfunctions in the above  *Will cause the Check Engine light to come on under normal (MODE I) operating conditions.

1. 2. 3. 4.

Trouble Code:	Detected Items:	Malfunction Caused By:	Check::
11*	Camshaft Angle Sensor circuit (CAS)	Either 1° or 120° signal is not entered for the first few seconds of engine cranking. Either 1° or 120° signal is not input often enough while the engine speed is higher then the specified RPM.	Harness and connector (if harness and connector are OK, CAS might be bad)
12	Mass Air-Flow Sensor circuit (MAS)	The MAS sensor circuit is open or shorted (abnormally high or low voltage is registered).	Harness and connector (if harness and connector are OK, MAS might be bad)
13	Engine Coolant Temp. Sensor	The Engine Coolant Temp. Sensor circuit is open or shorted (abnormally high or low voltage is registered).	Harness and connector Engine Coolant Temp. Sensor
14	Speed Sensor circuit	The Speed Sensor circuit is open or shorted.	Harness and connector Speed Sensor switch (reed switch)
21*	Ignition signal circuit	The ignition signal in the primary circuit is not entered during engine cranking or running.	Harness and connector Power Transistor Unit
26	Boost Pressure sensor (Turbo models)	The boost pressure sensor is open or shorted (abnormally high or low voltage is registered).	Harness and connector Boost pressure leaks Boost pressure sensor
31	ECU	ECU calculation function is failing	Replace ECU
32	EGR function	EGR valve does not operate (valve spring does not lift)	EGR valve EGRC-solenoid valve
33	O2 Sensor (left side)	The O2 Sensor is open or shorted (abnormally high or low voltage is registered).	Harness and connector O2 sensor Fuel pressure Injectors Intake air leaks
34	Detonation Sensor circuit	The detonation sensor circuit is open or shorted (abnormally high or low voltage is registered).	Harness and connector Detonation sensor
35	EGR Temp. Sensor	The EGR Temp. Sensor circuit is open or shorted (abnormally high or low voltage is registered).	Harness and connector EGR temp. sensor
42	Fuel Temp Sensor circuit	The Fuel Temp. Sensor circuit is open or shorted (abnormally high or low voltage is registered).	Harness and connector Fuel temp. sensor
43	Throttle Position Sensor circuit	The Throttle Position Sensor circuit is open or shorted (abnormally high or low voltage is registered).	Harness and connector Throttle position sensor
45	Injector leak	Fuel leaks from the injectors	Injectors
51	Injector circuit	The injector circuit is open	Harness and connector Injectors
53	O2 Sensor (right side)	The O2 Sensor is open or shorted (abnormally high or low voltage is registered).	Harness and connector O2 sensor Fuel pressure Injectors Intake air leaks
54	Signal circuit from the automatic transmission (A/T) (A/T models only)	The A/T communication line is open or shorted	Harness and connector

* Check items causing a malfunction of the CAS circuit first if both diagnostic codes 11 & 21 are displayed at the same time.

REV: 4-2-2000

DamonZ

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