Lambda Probe - VESPA 946 E4 EMEA 2021 Manual

Electrical system
1. Injection ECU
2. Control unit ground
Engine temperature sensor P0115 - open circuit or shorted to positive / shorted to negative.
Error cause
Open circuit or short circuit to positive: interruption of the circuit or excessive voltage at PIN 13 of the
control unit connector. Short circuit to negative: null voltage between PIN 13 and 15 of the control unit
connector.
Troubleshooting
Open circuit:
- Disconnect the connector of the control unit.
- Measure the resistance value of the sensor at different temperatures between PIN 13 and 15.
- Disconnect the sensor connector.
- Check the continuity of the wiring harness between the sensor connector and control unit connector:
Control unit PIN 13 - sensor PIN 1 and control unit PIN 15 - sensor PIN 2. If necessary, restore the
wiring harness.
- If the cabling is intact but the sensor resistance value is incorrect, this means that the sensor is faulty
and must be replaced, otherwise proceed with the checks.
Short-circuit to positive:
- With the sensor connector and the control unit disconnected, verify that the fault is a short with the
battery positive of sensor connector PIN 1(or control unit PIN 13) and restore wiring.
Short circuit to negative:
- Disconnect the sensor connector.
- Check the sensor connector PIN 1 ground insulation.
- If there is no ground insulation restore the wiring harness.
- If PIN 1 is insulated from the ground and the error persists, this means that there is a probable fault
in the control unit.

LAMBDA PROBE

Function
In charge of telling the control unit whether the
mixture is lean or rich.
Operation / Operating principle
Based on the difference of oxygen in the exhaust
fumes and the environment, this generates volt-
age which is read and interpreted by the injection
control unit. It does not require an external supply
source but, in order to work properly, it should
ELE SYS - 120
Vespa 946 E4-E5 EMEA-USA-ASIA (2021-)