2010 Citroen Other Engine Management Light

Tiny
GARYG1974
  • MEMBER
  • 2010 CITROEN
  • 2.2L
  • TURBO
  • RWD
  • MANUAL
  • 105,000 MILES
My Citroen Relay 2010 2.2DCI has the engine management light illuminated. I have had it checked with a diagnosis machine which came up with the faults "Inlet air temperature signal too high" and "Flowmeter signal value too high". The van has been driven (short distance) and I haven't noticed any drop in performance (the distance is too short to identify fuel economy). I wondered if anyone can point me in the right direction for fixing this, or a diagnosis that isn't going to cost hundreds of pounds like it would if I take it to a main dealer?
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Wednesday, July 23rd, 2014 AT 4:34 AM

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Tiny
CARADIODOC
  • EXPERT
I'm happy you appear to understand that fault codes never say to replace parts or that they're defective. It's the circuit that needs to be diagnosed. The parts referenced in a code are actually bad only about half of the time.

This is a perfect example of where there is likely to be a wiring problem. You have two totally different codes that would seem to be unrelated, but each one could be set by a break in that sensor's ground wire. On almost all cars, many sensors' ground wires are spliced together and share a common wire going back to the computer. That's where a break in one wire CAN result in setting multiple codes.

We don't have your car model here in the U.S, but the terminology suggests the sensors work the same way as on most other cars. The easiest one to diagnose should be the intake air temperature sensor. I've never seen anything other than a simple two-wire sensor. If you can find that, there's two voltage readings to take, but you have to do that without unplugging it. You can back-probe through the rubber seals. If it's unplugged, you will see 5.0 volts on the signal wire, and that will set the code you have. The acceptable range is 0.5 to 4.5 volts, with a little leeway. Reaching well over 4.5 volts is what triggers your code. Shorting the signal wire to ground will result in 0.0 volts on the that wire, and set the code "voltage too low".

The sensor is going to be somewhere that it sits in the incoming air stream, usually the intake manifold or the tube that connects the throttle body to the mass air flow sensor, (flow meter). In some cases the two sensors are incorporated into a single unit, and a ground wire problem could set both codes. A defective sensor could be the cause as well as a wiring problem. Most cars use two separate sensors so you'll have to find out which you have. My usual resources don't show those sensors so I can't tell.

If you do find 5.0 volts on the signal wire, next measure on the ground wire. That one should have 0.2 volts. If you 5.0 volts, that wire has a break between the sensor and the computer. If you find near 0.0 volts, the sensor is open, (has a break in it), or the connector terminals are stretched and not making good contact. Stretched terminals occur during previous service, not on its own. It's very rare for this temperature sensor to fail because there's just one simple part inside it.
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Wednesday, July 23rd, 2014 AT 10:27 PM

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