Nissan Sentra/Pulsar/NX 1982-1996 Repair Guide

Electronic Service Precautions


Do not disconnect the engine control module (ECM) harness connectors before the battery ground cable has been disconnected.
Make sure all ECM connectors are fastened securely. A poor connection can cause a high voltage surge from the coil and condenser, which will damage integrated circuits.
Keep the ECM harness at least 4 inches away from adjacent harnesses to prevent an ECM system malfunction due to external electronic interference.
Keep all parts and harnesses dry during service.
Before attempting to remove any parts, turn the ignition switch to the OFF position and disconnect the battery ground cable.
Always use a 12V battery as a power source.
Do not disconnect the battery cables with the engine running.
Do not press the gas pedal when starting the engine.
Do not race up the engine immediately after starting and just before shutdown.
Do not disassemble the ECM for any reason.
If the battery is disconnected, the memory will return to default Read Only Memory values.
Engine operation may vary slightly, but this is not an indication of a defective component.
If a 2-way radio is installed, keep the antenna as far as possible away from the ECM. Keep the antenna cable at least 8 inches away from the ECM harness, and do not let them run parallel for a long distance. Make sure the radio chassis is grounded to the vehicle body.
Make sure the ignition switch is OFF and the negative (-) battery connection is disconnected before connecting or disconnecting ECM connectors.
When performing ECM input/output signal diagnosis, remove the pin terminal retainer from the 20 and 16 pin connectors to make it easier to insert tester probes into the connector.
When connecting or disconnecting any terminals from the ECM, take care not to bend or break any pin terminals. Check that there are no bends or breaks on ECM pin terminals before attempting any connections.
Before replacing any ECM, perform the ECM input/output signal diagnosis to make sure the ECM is functioning properly or not.
After performing the electronic control system inspection, perform the ECM self-diagnosis and driving test.
When measuring the supply voltage of ECM-controlled components with a circuit tester, separate 1 tester probe from another. If the 2 tester probes accidentally make contact with each other during measurement, a short circuit will result, causing damage to the power transistor in the ECM.
All connector symbols in wiring diagrams are shown from the terminal side. The connector guides for male terminals are shown in black, and female terminals are shown in white in wiring diagrams.