Alas colour codes for wire do not help Citroen and Peugeot use alpha numeric,
My wiring diagram shows the CTS to be M1220 for the 5V and 1235 for the return signal.
So you may be on the right sensor.
5V feed is from ECU pin 37,
this is split to feed the CTS/intake temp sensor/MAP sensor/throttle position AND the power steering switch,
Which is something I suspect you've ignored till now.
Disconnect the power steering switch and retest for 5V.
Failing that it time to load test the wire harness.
I use a 6V motorcycle battery leads and an indicator bulb/holder.
Unhook the multi at the ECU and back probe T37 Bulb plugged into the sensor output and the return at the ECU plug to test battery ground,
bulb should glow bright,
make sure the bulb V is correct for 6V.
Or strip the harness back,
near as I can tell there's 4 splices on the 5V line from ECU T37 plus the power steering switch,
Any of which could be a high resistance connection.
Or If cash isn't a problem buy a set of "Load Pro" leads and learn to use them.
Definitive lead set for a multi meter,
Look up "LOAD PRO" on Youtube
This will test for high resistance which you do have,
there's no other explanation for 5V to become 2.5V
Posted Dec 13, 2015 (8 years ago)