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Ever seen a temp sensor like this?

Discussion in 'E30 (1984-1993)' started by mryflyguy, Jul 22, 2013.

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    mryflyguy

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    I've been experiencing a CEL flash every once in a great while while cruising on long distance trips. I was able to recover fault code #1223 from the ECU which indicates the coolant temp sensor is acting up. I asked the shop to replace it with a new, 2-pole PN 13621357414 but they discovered a 3-pole variety was installed instead. WTF? 2 wires from this connector go back to a relay mounted on the fuse box. The Tech said he followed one wire that headed off under the left front fender and thought it might be another fan relay or something. Does anyone know if this was a TSB fix for A/C cooling for something? Chances are disconnecting and cleaning that corrosion will take care of the fault codes but I'd really like to know what this is a solution for - and the part number for that 3-pole sensor! Isn't it fun working on 25 year old stuff?

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    MGarrison

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    Is that a 3-pole connector? Looks like a chewed-up 2-pole?

    I _think_ the two-pole(?) may have something to do with idle control, and the other one gives the signal for the dash gauge - from the ETM, it looks like they both run to the instrument cluster. There is also the 3-prong coolant temperature sensor in the radiator. BMW doesn't make a distinction in their parts descriptions via realoem.com, calling what you have pictured sensors, but in ETM diagrams, these appear to be labeled as "coolant temperature sender", which is how the Bentley manual describes them. Some potential for confusion there, and the ETM may not be perfectly specific in its labeling - ETM shows two senders wired into the instrument cluster, while the ECU (for Motronic 1.3 in this instance) gets an input from from a coolant temperature sensor through connector pin #45. It's not clear from the wiring diagrams exactly which sensor is the input to the ECU.

    The part number you've given is described on the Bavauto site as a fuel-injection temp. sensor, so perhaps that runs to the ECU, maybe via the instrument cluster - it might take several continuity tests to confirm that, but it's hardly of much importance. Which engine do you have? M10? M20? e or i?

    I'd say plug your two-pronger into the connector and see if it fits easily, and look closely to see if there's somehow some accommodation for 3 prongs. It may well be that somehow the wrong part got installed - yours looks similar to this one:

    http://www.fcpeuro.com/products/bmw...i-0280130056?gclid=CJ3BscqpxLgCFaY-MgodMy4AlA

    If the wrong part has been in there, it may be that the surprise is you haven't had a cel until now.
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    • Technical Service Advisor

    charlson89

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    If I remember this correctly one of those sensors if for the ECU and the other is for the gauge. I belive the sensor Mgarrison is talking about in the radiator is the switch for the aux fan to kick on.
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    mryflyguy

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    This is a stock M20 1989 325is. There are 2 temp sensors. The brown 2-pin connector is the sensor for the temp gauge. The shop changed this one and the temp gauge reads a little different. Actually, cleaning & cleaning the 3 prong connector may have addressed the CEL. Drove 2000+ miles to Monterey & back without indent. I did locate the PN and it's from a 850i. One of the leads can be traced along the fuse box => fender to the front/radiator. We suspect it's something installed for the aux cooling fan for A/C. As long as it works...

    Thx all!
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    Terry Sayther

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    That three wire sensor seems wrong---I'm used to seeing a 2 wire NTC [Negative Temp Coefficient] sensor there that feeds temp info to the DME to richen the fuel mixture when the engine is cold. Maybe somebody installed the three wire sensor to do something more than what BMW originally intended? In 1986 BMW had a campaign designed to make all the cars run better during warm-up and they installed a resister in one of the wires to the 2-wire sensor [greater resistance caused richer running]. I don't recall any 3-wire sensor being a part of that, but maybe there was some other factory campaign involved that I've forgotten.
    The one wire sensor is the temp gauge sender.

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