Fuel pump relay (Engine management system - V8)

In the event of an IACV signal failure any of the following symptoms may be observed: l Either low or high idle speed. l Engine stalls. l Difficult starting. l Idle speed in default condition.

There are eight IACV diagnostic checks performed by the ECM: l Output short circuit to earth – opening coil l Output short circuit to battery supply – opening coil l Output open circuit – opening coil l Output short circuit to earth – closing coil l Output short circuit to battery voltage – closing coil l Output open circuit – closing coil l Blocked IACV – rev/min error low (engine speed must be 100 rev/min less than the target speed, engine load less than 2.5 and the measured air flow more than 10 kg/h less than the expected air flow for a fault condition to be flagged). l Blocked IACV – rev/min error high (the engine speed must be more than 180 rev/min greater than the target speed and the measured air flow more than 10 kg/h greater than the expected air flow for a fault condition to be flagged).

Should a malfunction of the component occur, the following fault codes may be evident and can be retrieved by TestBook.

Fuel pump relay

The fuel pump relay is located in the engine compartment fuse box. It is a 4 pin normally open relay. Input from the ECM allows the fuel pump relay to control the electrical input to the fuel pump, regulating the fuel supply to the fuel injectors. When the ignition is switched on and the engine is cranked, the fuel pump relay is activated by the ECM, allowing the fuel system to be pressurised to 3.5 bar (52 lbf.in²). The ECM then deactivates the relay until the engine has started.

If the fuel pump runs, but the fuel pressure is out of limits, adaptive fuel faults will be stored.