MAP sensor - wiring check

[schmooser]

guys / gals  - Anyone able to give me the duffers guide to how I check the continuity in the wiring between the plug for the MAP sensor and the ECU?  I have a couple of error codes that point to the MAP sensor (5169 manifold pressure / boost sensor and 5282 intake air temp sensor).  I understand these are in the same sensor unit.  Just before I buy a replacement sensor I wanted to check the wiring loom.

 

Very much an enthusiastic amateur rather than competent mechanic, but I do know how to use a multimeter to check for continuity in wiring, I have located the sensor and visually checked for any obvious wiring issues at that end, I just need to know where the other end of the four wires going to the sensor are!  I assume they go straight to the ECU?

A bit nervous about messing about with the brains of the engine, but I am hoping there is a safe way of doing this by unplugging the the, no doubt large and complicated, connector at the ECU and identifying the appropriate pins I stand a fighting chance of checking the wiring.  Or will I be able to slot a safety pin into the reverse of the ECU connector, if someone can tell me which pin numbers to aim for.

 

(It appears to make no difference whether the sensor is connected or not, I have tried a number of times starting the engine with the sensor connected and disconnected, clearing codes etc.  but the same codes immediately come back whether the sensor is connected or not.)

 

[Breezy_Pete]

Would need year and engine code of your car to stand much chance of finding the pinout info.

[schmooser]

Whoops, sorry I forgot that bit . . . 2010 Skoda Superb Estate 2.0 TDi 140bhp, CFFB

[Breezy_Pete]

There's an intermediate (black) 4-pin connection apparently, on the gearbox somewhere.

MAP pin No.      Colour       Intermediate pin No.         colour          ECU pin No.

 

1                           Brown                          1                            brown/grey    66

2                           Yellow                          2                            red/grey         30

3                           grey/black                   3                              grey/black    17

4                           purple                          4                             purple            83

 

Test between MAP sensor and intermediate connector first.

[schmooser]

Thanks for the swift response Wino, I'll have another root around the engine this evening to see if I can get to that intermediate plug.

 

As for the ECU connections, are they accessible without disconnecting anything, i.e. pin in the rear of any connector?  

 

How 'safe' is disconnecting the ECU with ignition off?

[Breezy_Pete]

Don't know the answer to either of those questions, sorry.

[vborovic]

Based on my very recent experience on my car, you may actually have a problem with an air leak/vacuum coming from somewhere (air intake, pipes, hoses, head valve gasket, return PCV valve, ... any number of things), which is shown as an error related to the MAF, or rough idle, no other obvious causes ... I too was tempted to go wire by wire when I first started thinking about the potential cause, but based on some others' suggestions, decided to try the second route - which had paid off ... wires/connectors/harnesses are very rarely the cause, unless some unexplained or half-assed maintenance had been done on the car itself at some point in time

[schmooser]

Yeah, I was/am slightly concerned it may be a more complicated "problem nowhere near or related to the fault codes you're seeing" kind of thing!  Fingers crossed I may have tracked down the issue.

 

Just spent half an hour under the car trying to trace back the wiring loom to find the intermediate connector Wino referred to above.  Continuity fine from the sensor to the connector, but then . . . . voila . . . found a broken wire (brown)  on the other side of the intermediate connector.  Rain halted play, but the morning's job is to jury rig the connector to check that is indeed the culprit, then figure out how to make good a busted wire so close to the connector! 

 

So an optimistic thanks in advance Wino.

[Breezy_Pete]

That'll be it. Could always just bypass the connector pair for that wire. Try to waterproof whatever fix you do though, once its all working right.

[schmooser]

All fixed (for now), even managed to extract the contact from within the connector block, re-crimped and soldered for good measure, extra wire added and crimp connector to original offending wire and Bob's your uncle, no more warning lights and limp mode!

 

. . . oh, and copious amounts of insulation tape for good measure to keep the damp out!

[Andonov]

Can anybody post a photo of the MAP sensor location.

Many thanks.

[vborovic]

26 minutes ago, Andonov said:

Can anybody post a photo of the MAP sensor location.

 

Impatient, much?

 

 

[schmooser]

Can't take a photo, but mine was located at bottom of the engine bay on one of the the inch or so diameter air hoses at the front of the engine on the off side (right hand side, it's a mk2 140bhp 2.0tdi).  You can see it if lay on your back slide your way in and look up!