Test Point 4

TEST POINT 4
Oxygen sensing range 2 and range 1, cylinders 1 - 3

DTC 26, 27, 28

Fault: Lean limit
mixture is so rich that the control is at its lean limit.

Fault area: Fuel pressure too high or injection valve leaks.

Remedy: 1. Check fuel pressure.
2. Check fuel pressure regulator, vacuum connection and fuel return line.


Fault: Rich limit
mixture is so lean that the control is at its rich limit.

Fault area: - Intake system leaks
- Fuel pressure too low
- Injection valves fouled
- Fuel pump delivery too low

Remedy: 1. Check exhaust system for leaks.
2. Check intake system for leaks.
3. Check fuel pressure.
4. Check fuel pump delivery.
5. Clean injection valves in ultrasound cleaning device or replace.