Nissan Altima OBDI ECU Pinouts

Nissan Altima OBDI ECU Pinouts

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Today we’ll be taking a look at the ECU pinouts for a 1993-1995 Nissan Altima, the OBDI version of course. This car came with the well known KA24DE, and is a commonly modified car for that era.We’ll be covering all pertinent pinouts in relation to this ECU, if you have any questions leave them below.

1993-1995 Nissan Altima OBDI ECU PINOUTS

altima

POWER AND RELAYS

Wire # Name Information
38 Power Supply for ECM This power comes from the ECM relay to energize the ECM, and the MAF and CMP sensors. It is available when the ignition switch is set to ON. This wire is also paired with pin 47.
47 Power Supply for ECM This power comes from the ECM relay to energize the ECM, and the MAF and CMP sensors. It is available when the ignition switch is set to ON. This wire is also paired with pin 38
104 Fuel Pump Relay This ECU provided ground enables the fuel pump relay during fuel pump priming (5 seconds) or while the engine is running. The only time is goes to battery voltage is after the fuel pump priming function.

ENGINE INPUTS

Pin # Name Information
32 Vehicle Speed Sensor The vehicle speed sensor is installed in the transaxle. It sends a signal to the speedometer, which will in turn sends it out to the ECU, ATCU, and cruise control unit.
20 Throttle Position Sensor This DC voltage varies with the position of the throttle plate. The ECU sends a 5 volts reference to this sensor and then senses how much of it comes back from this line. This voltage represents the angular degrees of opening (max=90 degrees).
16 Air Flow Meter This DC voltage signal carries the representation of the amount of intake air flow sensed by the MAF hot-wire. The value varies with engine speed and is sent to the ECU for calculating fuel and ignition 0.8 – 3.0V
93-94 Nissan Altima ECU 16 OR Mass Airflow Sensor QA+ intake air flow sensed by the MAF hot-wire. The value varies with engine speed and is sent to the ECU for calculating fuel and ignition requirements.
27 Knock Sensor This wire is held steady at about 2.5V. When an audible knock is heard it will inform the ECU of the event. The level of knock spikes determine the knock intensity.

ENGINE VITALS

Pin # Name Information
31 Camshaft Position Sensor (Position
signal)
The pulse signal represents the 1° rotation of the crankshaft. There are 360 slits of a photo diode/sensor disc (Optronic) inside the distributor. This wire is also paired up with pin 40
30 Camshaft Position Sensor (Reference
signal)
The pulse signal represents the TDC of all cylinders. The #1 cylinder is differentiated by a long pulse width. This signal is referred to a 180º signal. It originates from 4 slits of a photo diode/sensor disc (Optronic) inside the distributor. This wire is paired with pin 22 and has the same functionality.
1 Ignition Signal This pulse signal drives the base of the ignition power transistor and switches it ON and OFF. The power transistor will then in turn cycle the primary side of the ignition coil ON and OFF.

OTHER ECU ESSENTIALS

Pin # Name Information
2 Tachometer This pulse signal drives the tachometer in the instrument cluster.
4 ECM Relay Ground (self-shutoff) The ECU will provide this ground to the ECM Relay when the ignition switch is set to ON (sensed on pin 36). When the ignition switch is switched OFF, power will drop out from pin 36 and the ECU will then provide battery voltage to this relay to put the ECU in standby. It can take a few seconds for the ECU to go into standby.
21 ECM Sensor Ground The ECU provided ground goes to various sensors. The original ground comes from two engine grounding points located at the topside of the upper intake manifold.
35 Neutral Position Switch The ECU senses the ground from this switch when the transmission in either in Park or Neutral. Will need to be bypassed if switching to a manual transmission.
104 Fuel Pump Relay This ECU provided ground enables the fuel pump relay during fuel pump priming (5 seconds) or while the engine is running. The only time is goes to battery voltage is after the fuel pump priming function.
36  Ignition Switch The ECU senses the ground from this switch when the transmission in either in Park or Neutral.

That does it for our Nissan Altima ECU pinout, please let us know if you have any questions by commenting below.

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