Nissan Sentra Service Manual: On Board Diagnostic (OBD) System of Engine and CVT
The ECM has an on board diagnostic system. It will light up the malfunction indicator lamp (MIL) to warn the driver of a malfunction causing emission deterioration.
CAUTION:
- Be sure to turn the ignition switch OFF and disconnect the negative battery cable before any repair or inspection work. The open/short circuit of related switches, sensors, solenoid valves, etc. will cause the MIL to light up.
- Be sure to connect and lock the connectors securely after work. A loose (unlocked) connector will cause the MIL to light up due to the open circuit. (Be sure the connector is free from water, grease, dirt, bent terminals, etc.)
- Certain systems and components, especially those related to OBD, may use a new style slide-locking type harness connector. For description and how to disconnect, refer to PG-42, "Description".
- Be sure to route and secure the harnesses properly after work. The interference of the harness with a bracket, etc. may cause the MIL to light up due to the short circuit.
- Be sure to connect rubber tubes properly after work. A misconnected or disconnected rubber tube may cause the MIL to light up due to the malfunction of the EVAP system or fuel injection system, etc.
- Be sure to erase the unnecessary malfunction information (repairs completed) from the ECM and TCM (Transmission control module) before returning the vehicle to the customer.
Precaution for Procedure without Cowl Top Cove.r.
When performing the procedure after removing cowl top cover, cover
the lower end of windshield with urethane, etc to prevent damage to
windshield.
...
General Precautions
Always use a 12 volt battery as power source.
Do not attempt to disconnect battery cables while engine is
running.
Before connecting or disconnecting the ECM harness connector,
turn ignitio ...
Other materials:
B142A Ignition voltage
Description
DTC B142A IGNITION VOLTAGE
Ignition voltage is supplied to the air bag diagnosis sensor unit when the
ignition is in the ON position. The air
bag diagnosis sensor unit will monitor for low or high ignition voltage.
PART LOCATION
Refer to SRC-5, "Component Parts Location" ...
P0171 Fuel injection system function
DTC Logic
DTC DETECTION LOGIC
With the Air/Fuel Mixture Ratio Self-Learning Control, the actual mixture
ratio can be brought closely to the
theoretical mixture ratio based on the mixture ratio feedback signal from the
A/F sensors 1. The ECM calculates
the necessary compensation to correct th ...
Hvac branch line circuit
Diagnosis procedure
1.Check connector
Turn the ignition switch off.
Disconnect the battery cable from the negative terminal.
Check the terminals and connectors of the a/c auto amp. For damage, bend
and loose connection (unit
side and connector side).
Is the inspection result normal? ...
