DTC P.0193 Fuel rail pressure High Input

S-Type
1

I have a P.0193 (Fuel Rail Pressure High Input)error code and found the following on page 1436 Repair Manual.

P0193 Concern with fuel rail
pressure sensor
(high voltage/high
pressure)
Fuel rail pressure sensor to ECM
wiring (supply/sense) short
circuit to each other
Fuel rail pressure sensor to ECM
sense circuit; short circuit to
high voltage
Fuel rail pressure sensor to
splice in sensor ground circuit;
open circuit
Fuel rail pressure sensor failure

Just wondering if anyone has worked on this area before?
I notice that there is an adjusting screw on the top of the unit.
I’m thinking of fitting a new regulator…anyone have a part number please?
My car is 2002.5 S Type 4.2 V8 NA Viv M52021
High mileage vehicle. Denso unit fitted Looks like 135000-8100 and ZW(?)93 9E456 AA

2

The S-Type has a ‘returnless fuel system’. There is no fuel pressure regulator as the pump speed is PWM controlled to vary the pump’s delivery. The fuel pressure and temp sensors at the rail report to the ECM.

A replacement sensor will probably be the most cost effective way to determine the fault.
The circuit (wiring) could also be at fault but a sensor is a ‘quick&easy’ way to tell?

3

Thanks Bob for your reply. I’m a bit confused now as page 1432 of the 2002.5, 4.2 V8 manual shows “item 1 Fuel Pressure Regulator”

It goes on to say

“Fuel is supplied at high pressure to the fuel injectors via a fuel supply manifold which incorporates fuel injectors a fuel pressure regulator and a fuel temperature sensor-“

However the DTC , P0193 “Possible Causes” only refers to Fuel rail pressure sensor.

Can you clarify for me please.

Dave

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4

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Not sure these pdf’s will attach ???

5

The JEPC refers to that as a Fuel Pressure Sensor. I guess it could ‘regulate’ the pressure indirectly by relaying info to the ECM? It does NOT directly regulate the pressure like a system with a fuel return. That ‘dumps’ fuel back to the tank with a spring and vacuum system.

The pump on a mechanically regulated system runs at speed all the time whereas the returnless system varies the pump speed to regulate pressure.

6

Thanks again Bob. Looks like the names may be interchangeable? But thanks for explaining how it works.

I notice that Jagbits(USA) refer to Part AJ87977 as – “Fuel pressure sensor regulator(Transducer)”

So… My next question is. Am I really getting high fuel rail pressure or is it just a faulty message from the sensor?

And how do I fix the issue if the pressure is in fact too high?

I cleared the DTC but the error code returned.

Happy to get your response but I have taken your suggestion and have a new sensor on order so I’ll see what happens when I fit it.

Kind regards

Dave

7

I think you can monitor the actual fuel pressure with WDS or IDS (maybe some other dealer level diagnostics?) using the DATALOGGER feature but it has been years since I used WDS/IDS everyday.

Probably the easiest is to replace the ‘transducer’ and see if that fixes the fault.

8

Ok…I’ll wait and see once I receive and fit the new unit.
Cheers

9

Thanks for earlier advice. I have fitted the new sensor.
No DTC showing for this function now.
I’ve noticed some improvement through the low rev range.
Fuel economy has improved a little, but I’m running a 10w 40 semi synthetic oil at 350,000km. I reluctantly try to stay off the throttle at low speed as too much enthusiasm will produce a “James Bond smoke screen”
Kind regards.