Testing Cautions

Before connecting or disconnecting ECU harness connector to or from the ECU, be sure that ignition switch is in the "OFF" position and negative battery cable is disconnected or damage to the ECU may result. This is important because battery voltage is applied to the ECU even when the ignition switch is in the "OFF" position.

When performing an ECU input/output signal inspection, remove pin terminal retainer from connectors. This will make probing of the connector pins much easier and safer.

When connecting or disconnecting pin connectors from the ECU, take care not to bend or break any pin terminals.

Before replacing ECU, perform the ECU input/output signal inspection to be sure ECU is malfunctioning.

Fig 1: Modes 1 & 2 Mixture Feedback Control Monitors A & B Chart

Fig 2: Key to Symbols

ECU DIAGNOSTIC CODES CHART

Codes

Models

Component

All

Crank Angle Sensor

All

Airflow Meter

All

Coolant Temperature Sensor

All

Ignition Signal

Pulsar & Sentra

Idle Speed Control

All Except Pulsar & Sentra

Fuel Pump

Pulsar NX, Sentra & Van

Exhaust Gas Sensor

300 ZX Turbo

Denotation Sensor

⁽¹⁾

Fuel Temperature Sensor

Pulsar & Van

Throttle Sensor Circuit

Van

Injector Circuit

Pulsar & Sentra

⁽³⁾

⁽²⁾

⁽¹⁾	On Maxima, 200SX and 300ZX models, code 41 is fuel temperature sensor circuit. On Pulsar, Stanza, Stanza Wagon and Sentra code 41 is the air temperature sensor circuit.

⁽²⁾	On Maxima, 200SX, 300ZX models, fuel temperature sensor circuit is okay. On Van models, injector circuit is okay. On Pulsar and Sentra models, mixture ratio feedback control circuit is okay.

⁽³⁾	Mixture ratio feedback is slipping out.