Diagnostics
The most important parameter of the fuel pressure control system is not available from the diagnostic level. The only way to read this parameter is to measure it physically with a PWM meter. The PWM value should be within 15% during engine braking to 40% at full load. If the system is fully efficient, the value does not exceed 32%. At idle it is about 17% depending on the engine temperature. On a hot engine the values are about 2-3% higher than on a cold one, accordingly 35% and 20%.
During start-up, the PWM is 70% in order to reach the working pressure as quickly as possible.
A common voltmeter connected to the center line of the pressure sensor can be used to measure the fuel pressure. The correct values are about 0.6V when the ignition is turned on, 1.65V at idle and 3.2V maximum indications. This corresponds to a pressure of 5 bar, 50 bar and 110 bar.
If the PWM value reaches 45% for more than 3 seconds, which means that the injection system does not reach the required pressure within 3 seconds, the P1191 fault and a spanner light will be displayed. Similarly, if the PWM drops to 15% and the injection system does not reduce the pressure to the required value within 1 second, the P1191 fault and a spanner light will be displayed.
Check Engine light
Check Engine light indicates damage to the ECM circuits or the reading is outside the acceptable range. This type of damage should always be repaired first.
Spanner light
Spanner light indicates exceeding the permissible operating parameters beyond the specified range.