The other day my 95 850 t just dint wanna start i checked for codes and i have 3-1-4 code
so i checked if the harness was good and here is where it gets tricky

i back probed the cmp and i have 10 volts in the y/r wire
steady 5 in the blue wire while cranking and with a key on
and ground is there
then i unpluged the connector and checked the wires on the computer side and it shows the same as above
what i dont understand is why is there 5 volts in the blue wire when i thought that was the signal from the cmp to the computer ???

thanks in advance..

 

The signal on the Blu/Ylw wire on your Cam Position Sensor (CMP) should alternate between 0 and 5V as you crank the starter. Either the sensor is bad or (yikes!) the cam isn't turning?

Take the sensor off, key ON, turn it by hand and note the voltage on the Blu/Ylw (terminal 2 i believe); if it stays at 5V then replace the sensor.

Below from volvo manual:
====================

5) Remove intake hose. Bend aside rubber sleeve on CMP
connector. Connect voltmeter between connector terminal No. 2 and
ground. See Fig. 4. Operate starter motor. If voltage reading varies
between 0-5 volts, go to step 7). If voltage reading does not vary
between 0-5 volts, go to next step.
Fig. 4: Identifying Camshaft Position Sensor (CMP) Terminals
Courtesy of Volvo Cars of North America.
6) Connect voltmeter between CMP connector terminal No. 3 and
ground. Turn ignition on. About 10 volts should be present. Turn
ignition off. Connect an ohmmeter between CMP connector terminal No. 1
and ground. Ohmmeter should show about zero ohms. If voltage supply
and ground are okay, repeat test using new CMP. If voltage supply and
ground are not okay, reconnect intake hose and go to step 9).
7) If voltage reading varied between 0-5 volts in step 5),
disconnect power stage connector at ignition coil. Bend back rubber
sleeve on connector. Check ground supply by connecting ohmmeter
between connector terminal No. 1 and ground. See Fig. 5. Ohmmeter
should indicate zero ohms. Check voltage supply by connecting
voltmeter between terminal No. 3 and ground. Turn ignition on. Battery
voltage should be present.
Fig. 5: Identifying Power Stage Connector Terminals
Courtesy of Volvo Cars of North America.
8) Check power stage control signal by connecting voltmeter
between terminal No. 4 and ground. Operate starter motor. Voltmeter
should indicate .7-1.3 volts. If ground, voltage and control signal
are okay, repeat test using new power stage. If ground connection and
voltage are faulty, check wiring. If control signal is not present, go
to next step and check ECU input and output signals.