[urq] Coolant temp sensor and duty cycle q's

n-engelbert at terrans.net n-engelbert at terrans.net
Mon Dec 1 10:00:36 EST 2003

I went to pick up the ECU coolant temp sensor that I had ordered 035 919
501, and it's very visibly different than the one that is currently in the
car.  The replacement has sort of a button connector on top whereas the one
currently in the car has a spade terminal.  Both have white tops.  I
haven't removed the one in the head, so I don't know the thread size/pitch
on it, but it looks like it will take at least a 17 mm socket, maybe 19, to
remove.  The new sensor is much smaller, maybe 13 mm socket, with a m10x1
threaded portion.

The current sensor is most definitely dead.  The resistance to ground, with
the ecu lead disconnected, is open circuit.

Now for some duty cycle readings:  Taken with engine warm, O2 connected,
temp sensor connected (although open circuit).  At warm idle, duty cycle
either 20 or 80%.  Idle switch closed, full throttle switch closed, 21 or
79%.  Idle switch disconnected, full throttle closed, 21 or 79%.  Values
are with duty cycle meter connected both ways to the connector by the
ignition coil.

These all look to be that of a cold engine upon cranking, or are adjusted
WAY off.  O2 sensor voltage through all of this is about 0.74V, pretty

This is most probably the reason that my car stumbles while warming up, the
only question now is why the duty cycle doesn't change?

Can I assume that a new temp sensor will change this?  If so, is the one
with the round connector on top the one I want, or is there a part with a
spade connector that I just can't find in the family album under any car?


Nathan Engelbert
83 UrQ 900453

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