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1997 Nissan Altima ECUby jserrano (www.nissanclub.com)Rev. 0.3PinColorNameSymbolDescription1WIgnition SignalIGNThis pulse signal drives the base of the ignition power transistor andswitches it ON and OFF. The power transistor will then in turn cyclethe primary side of the ignition coil ON and OFF.2Y/RIgnition CheckIGNCKThis ignition signal is a feedback for the ECU to monitor the status ofthe primary ignition system.3L/BTachometerTACHOThis pulse signal drives the tachometer in the instrument cluster.The ECU will provide this ground to the ECM Relay when the ignitionswitch is set to ON (sensed on pin 38). When the ignition switch isswitched OFF, power will drop out from pin 38 and the ECU will thenprovide battery voltage to this relay to put the ECU in standby. It takea few seconds for the ECU to go into standby.No pinout connection.45W/GECM Relay Ground (self-shutoff)N/A ?SSOFF6BlackECM Ground ?GNDThis ECU ground comes from two engine grounding points locatedat the topside of the upper intake manifold.ATCKThis line is used by the ATCU to inform the ECU when it hasencountered a problem. In which case, the ATCU will set the O/Dlight while the ECU with set the Check Engine light.7G/OR8B/Y9LG/RA/T Check SignalFuel Pump RelayFPRAir conditioning Triple-pressure switchARCONSignal6.0 -16.0VThis ECU provided ground enables the fuel pump relay during fuelpump priming (5 seconds) or while the engine is running. The onlytime is goes to battery voltage is after the fuel pump priming function.This signal informs the ECU when the A/C liquid tank is under- orTriple-pressure position,over-pressurized. It also controls the cooling fans operation toON: 0.1V,equalize the pressure buildup.OFF: 6.0V - 16.0V

1011121314151617BLGLG/RY/L18OR19B202122Cooling Fan Relay (high speed)Cooling Fan Relay (low speed)Air Conditioner RelayGND-IRFRHThe ECU will provide ground to this relay when it needs to operatethe cooling fans at high speed. Also, it will provide battery voltage tothis relay when it needs to turn OFF the cooling fans.RFRLThe ECU will provide ground to this relay when it needs to operatethe cooling fans at low speed. Also, it will provide battery voltage tothis relay when it needs to turn OFF the cooling fans.ACRLYThe ECU will provide ground when both the A/C and blower fanswitches are turned ON. It will provide battery voltage when it needsto turn OFF the relay.Malfunction Indicator LampLED-RECM GroundGND-IG/BStart SignalSTSWLG/BAir Conditioner SwitchA/C SWG/OR Park/Neutral Position Switch23W24BR/R25ECM GroundThe ECU provided ground goes to various sensors. The originalground comes from two engine grounding points located at thetopside of the upper intake manifold.G/YPNPSWThrottle Position SensorTVI1Automatic Transmission Data Line #1DT1Power Steering Pressure SwitchPWSTThis wire turns on the MIL. It flashes when the ECU is set todiagnostic mode, set to oxygen sensor testing, or the engine ismisfiring. It is normally turned OFF by applying battery voltage.The ECU provided ground goes to various sensors. The originalground comes from two engine grounding points located at thetopside of the upper intake manifold.The ignition switch provides battery power to this pin to tell the ECUto go into START mode.This signal informs the ECU when the A/C is switched ON ( 0.1V).The ECU response by increasing idle speed to improve idling andA/C switch position,reduce emissions. During heavy engine load, the ECU will turn OFF ON: 0.1V,the A/C clutch relay to disengage the A/C clutch.OFF: 11-14VThe ECU senses the ground from this switch when the transmissionin either in Park or Neutral.This DC voltage varies with the position of the throttle plate. TheECU sends a 5 volts reference to this sensor and then senses howmuch of it comes back from this line. This voltage represents theangular degrees of opening (max 90 degrees).This A/T data transmission line #1 is used in conjunction with DT2 &DT3 to control the smooth shifting up and down of the AT duringhard acceleration and deceleration.The ECU senses this switch to detect when the steering wheel isturning at low speeds. It will quickly increase the idle to compensatefor the additional engine load.Gear selector position,Neutral: 0.1V,not-Neutral: 5.0V0.3 - 4.0V6 - 8VSteering wheel position,Turning: 0.1V,Straight: 4.4V

2627Y/GVehicle Speed SensorVSPThe vehicle speed sensor is installed in the transaxle. It sends asignal to the speedometer, which will in turn sends it out to the ECU,ATCU, and cruise control unit.Intake Air Temperature SensorTAL/RAutomatic Transmission Data Line #2DT2BR/WAutomatic Transmission Data Line #3DT3This DC voltage varies with the intake air temperature. The voltagedecreases as the intake air temperature rises. This sensor is onlyused for diagnostics, never for air/fuel mixture control.This A/T data transmission line #2 is used in conjunction with DT1 &DT3 to control the smooth shifting up and down of the AT duringhard acceleration and deceleration.This A/T data transmission line #3 is used in conjunction with DT1 &DT2 to control the smooth shifting up and down of the AT duringhard acceleration and deceleration.This DC voltage varies with the position of the throttle plate andrepresents the angular degrees of opening (max 90 degrees). Thissignal is solely provided for the ATCU. .28L293031323334353637W/RThrottle Position SensorTVI138B/RIgnition SwitchIGNSW39BECM GroundGND-CThe ignition switch provides battery power to this pin to tell the ECUthat the ignition switch is ON or STARTing.The ECU provided ground goes to various sensors. The originalground comes from two engine grounding points located at thetopside of the upper intake manifold.REFThe pulse signal represents the TDC of all cylinders. The #1 cylinderis differentiated by a long pulse width. This signal is referred to a180º signal. It originates from 4 slits of a photo diode/sensor disc(Optronic) inside the distributor. This wire is also paired up with pin44.POSThe pulse signal represents the 1 rotation of the crankshaft. Thereare 360 slits of a photo diode/sensor disc (Optronic) inside thedistributor. This wire is also paired up with pin 45.GND-CThe ECU provided ground goes to various sensors. The originalground comes from two engine grounding points located at thetopside of the upper intake manifold.40414243LCamshaft Position Sensor (Referencesignal)LCamshaft Position Sensor (Positionsignal)BECM Ground0 - 5.0V6 - 8V0V0.4 - 5.0V

4445LCamshaft Position Sensor (Referencesignal)LCamshaft Position Sensor (Positionsignal)CMP1The pulse signal represents the TDC of all cylinders. The #1 cylinderis differentiated by a long pulse width. This signal is referred to a180º signal. It originates from 4 slits of a photo diode/sensor disc(Optronic) inside the distributor. This wire is also paired up with pin40.CMP2The pulse signal represents the 1 rotation of the crankshaft. Thereare 360 slits of a photo diode/sensor disc (Optronic) inside thedistributor. This wire is also paired up with pin 41.47ORMass Airflow SensorQA When the ECU enters O2 sensor mixture feedback called closedloop, it will continuously monitor that this sensor's output voltageswings between 0 -1 volts. When the engine is running atstoichiometric (AFR 14.7), it should swing at least five (5) timesacross the centerline of 0.5 volts (500 mV) within ten (10) seconds.Changes outside these parameters causes the ECU to identify areasneeding long term fuel trim corrections.This DC voltage signal carries the representation of the amount ofintake air flow sensed by the MAF hot-wire. The value varies withengine speed and is sent to the ECU for calculating fuel and ignitionrequirements.48WMass Airflow Sensor GroundQA-This ground is provided by the ECU solely for the MAF.49R/Y50B51L/OR46WFront Heated Oxygen SensorO20.8 - 3.0V0.005 - 0.02VApproximately 5.0V5253WWThrottle Position Sensor Power Supply TPSPSECM Sensor GroundGND-AThis is the 5V reference that the ECU provides to the TPS.The ECU provided ground goes to various sensors. The originalground comes from two engine grounding points located at thetopside of the upper intake manifold.Engine Coolant Temperature SensorTWThis DC voltage varies with the engine coolant temperature. Thevoltage decreases as the coolant temperature rises.O2SRThis signal provides the ECU and indication of the state of the three- 0 - Approximately 1.0Vway catalytic (TWC) converter funtionality.With a fully warmed upsystem this signal will swing and follow what the front oxygen sensoris doing.RGC/SThe CKP provides the ECU a crank rotation signal so that it canmonitor for an engine misfire. It compares the CMP reference signalto determine which cylinder caused the misfire. This is purely usedfor diagnostic and do not affect air/fuel mixture control.Rear Heated Oxygen SensorCrankshaft Position Sensor0 - 5.0V

54WKnock SensorKSThis wire is held steady at about 2.5V. When an audible knock isheard it will inform the ECU of the event. The level of knock spikesdetermine the knock intensity.5657ORPower Supply for ECMVBThe ECU senses the rear window defogger relay to determine whenthe defoggers are operating so that it can make adjustments to theadded electrical load.This power comes from the ECM relay to energize the ECM, and theMAF and CMP sensors. It is available when the ignition switch is setto ON. This wire is also paired with pin 61.585960ORData Link Connector for GSTKLINEThis line is used by an Onboard Diagnostic II (OBD2) generic scantools to read out ECU engine operating parameters.5561L/RORRear Window Defogger RelayR/DEFApproximately 9VPower Supply for ECMVBEGR Temp SensorEGRTSThis power comes from the ECM relay to energize the ECM, and theMAF and CMP sensors. It is available when the ignition switch is setto ON. This wire is also paired with pin 56.The EGR temperature sensor is provided on California engines ormodels with manual transmission. It is used to diagnose EGR flow 1.0V @ 1500 rpm withrelated issues.EGR valve fully openIntake Air Temperature SensorTAThis DC voltage varies with the intake air temperature. The voltagedecreases as the coolant temperature rises.62R/L63L64Y/BCONSULT Data Link Connector (Rx)SCIRXThis is the data line used by the ECU to receive serial data from aNissan CONSULT device. 0.1V656667Y/RCONSULT Data Link Connector (Tx)SCITXThis is the data line used by the ECU to transmit serial data from aCONSULT device. 4 - 9V6869YCONSULT Data Link Connector (Clk)SCICLThis is the data line used by the ECU to clock serial data to and froma CONSULT device. 3.5V70WPower Supply (Back-up)BATTThis battery power is provided to the ECU at all times. This wire isalso paired up with pin 113.101SBIACV-AAC ValveISCThis is the Idle Air Control Valve - Auxiliary Air Control Valve dutycycle signal that controls the idle speed.102BRInjector #1INJ#1This is the ECU provided pulsewidth signal for injector #1.0 - 5.0V