ME9 / P2251 00

Read the instructions below then start the fault diagnostic procedure.

Symptom: Malfunction Indicator Lamp

P2251 00

Fault symptom

Malfunction Indicator Lamp

On-board diagnosis

Type of diagnosis:

Continuous

Enable criteria:

Battery voltage should be between 10.7 and 16 Volts.

Engine running.

Running with even load for at least 30 seconds.

Voltage across Nernst cell is 1.36 - 1.48 V for more than 5 seconds.

Fault criteria:

Voltage across the Nernt cell does not change (control module detects this because preheating is constantly on).

Open circuit on the lead between control module pin A52 and sensor pin 2.

Checking the wiring harness

Move the wiring harness at several spots and in several directions to reveal intermittent breaks and short-circuits. Check switches, connectors and crimp connections for oxidation, retracted pins and pin clamping force.

Diagnostic help

Diagnosis regards:

Electrical fault in connecting leads or component.

Functions in the diagnostic tool related to the fault:

Test value:

•	Requested O2S1 Lambda

•	O2S1 lambda

•	O2S1 Pump Current

•	Preheating O2S 1

•	Short Term Fuel Trim Status

•	Closed Loop

•	Total Fuel Trim

(See also description of readings/activations in diagnostic tool)