Have a 2006 V6 convertible that won't run with the FRPT sensor connected. Had it since new and love it.
Replaced the FRPT sensor, the connector and the PCM. Tested the wiring as best I could. Still get a P0183 and P0193 code. If I connect the FRPT sensor, sometimes the fuel pressure drops and the engine stalls. Been through all the threads, and documentation and diagnostic procedures I could come up with.
When I disconnect the wire coming from pin one 1 FRP (Fuel Rail Pressure) only and measure the voltage coming from the sensor it is correct according to the following chart.
FRP SENSOR VOLTAGE AND PRESSURE SPECIFICATIONS
Voltage / Pressure (kPa) / Pressure (psi)
4.5 482 70
3.9 413 60
3.4 344 50
2.8 275 40
2.2 207 30
1.6 138 20
1.1 69 10
0.5 0 0
However, when I measure the voltage on pin 1 and 3 at the FRPT conector coming from the PCM I get 5 volts always. When connected, the lower voltage from the sensor only pulls the 5v down slightly resulting in a very high fuel pressure reading from the PCM. As a result the PCM slows the fuel pump in a attempt to lower the pressure and the engine stalls.
Pin / Circuit
3 FRT (Fuel Rail Temperature)
1 FRP (Fuel Rail Pressure)
4 SIGRTN (Signal Return)
2 VREF (Reference Voltage)
I get no continuity between pin 1 and 2, so I have no clue where the 5 volts on pin 1 is coming from. Thought it was a bad PCM, so I replaced that, 5 volts is still there.
Pin 2 is of course always 5 volts, and pin 4 has no voltage between it and ground. 5v between pin 4 (Signal Return) and everything else (pins 1,2 and 3).
If I display the fuel pressure from the PCM with my scan tool and mess with the harness, FRPT and PCM connectors, I see no change in the erroneously high fuel pressure indication. - Reads as high as 60PSI - so I think that is impossible.
I noticed others post fuel pressure reads high from the pcm when the FRPT is disconnected, so is there supposed to be 5v on pins 1 and 3 coming from the PCM?
Any ideas? Seems I have literally replaced everything (except the harness)
Also, I can't find connector diagrams for the PCM anywhere. - even checked the workshop manuals posted online, can find schematics, but no pinouts or diagrams / drawings for the PCM connectors.
Am up against a wall, and don't know of any shop including the dealer that could help with this one.
Any help would be greatly appreciated!!