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Old 8th May 2017, 22:12   #1
Geoff130
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Default ECU Repair?

My car 1.8K recently started showing unusually high coolant temperatures (102 C) on my Intravee but the coolant level was fine and not excessively hot. It then started reading -128 c which is the same result as disconnecting the sensor. I tried a spare sensor but the problem returned after a few miles. I have checked the resistance from the ECU plug and it showed 2.7k ohms. No amount of twisting the sensor plug would change it. The sensor itself is 2.7k at room temperature. Putting the original back restored the high readings and it now sits at 127C again with the coolant system showing no signs of distress. A laser temperature sensor on the top hose read 60 C. Fitting a brand new sensor still reads 127C when warm. It seems my ECU is faulty, is there any way to program a spare unit to match my old one so the EWS recognises it? Could it be re-calibrated?
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Old 8th May 2017, 22:33   #2
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contact marinabrian .hell be able to help you.
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Old 8th May 2017, 22:36   #3
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Yes the MEMS can be swapped out if you are prepared with a solder station you could swap its eeprom out or program a virgin chip on your replacement from a scrappy. Then would need a little session with T4 to complete the programming to match you car. Alternatively marinabrian will sort it out for you and will no doubt be along soon
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Old 9th May 2017, 08:12   #4
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Default MEMS3 Wiring Diagram

One other thing to check out would be to reconnect the sensor to the engine harness and then remove the connector C0914 (large 52 pin) at the MEMS ECM in the plenum itself and check for continuity and resistance readings.

Large connector C0914 - 52 pin

Pin-7 Pink/Black sensor ground – input

Pin-33 Pink/Green sensor signal – input

ECU Coolant Temperature (°C): Shows the current temperature of the engine coolant. The measurement is taken using the engine coolant temperature sensor. The ECU will automatically calculate a safe default temperature if the sensor reading is implausible. The reading may continue to change even with a faulty or disconnected sensor.
•Input Coolant Temperature (°C): Shows the actual reading directly from the sensor. No processing or checking is done on this value so the reading will directly indicate any faults present in the sensor or input circuit. By comparing this reading with the ECU processed version it is possible to see when the ECU is using a default value.

https://blackbox-solutions.com/help/SM003.html
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File Type: jpg MEMS3_0776.jpg (129.8 KB, 21 views)
File Type: jpg MEMS3_0775.jpg (129.3 KB, 14 views)
File Type: jpg MEMS3_0774.jpg (127.5 KB, 12 views)

Last edited by Lovel; 10th May 2017 at 08:07.. Reason: Added in MEMS3 Wiring Diagram
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Old 15th May 2017, 00:00   #5
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Thanks for the replies, I thought you may be interested to hear that the eventual culprit was a failed power steering load sensor! I found it by removing every pin on the large ECU connector apart from IGN, coolant temperature sensor, coils and injectors then adding the sensors until the fault returned.
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Old 15th May 2017, 06:18   #6
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Quote:
Originally Posted by Geoff130 View Post
Thanks for the replies, I thought you may be interested to hear that the eventual culprit was a failed power steering load sensor! I found it by removing every pin on the large ECU connector apart from IGN, coolant temperature sensor, coils and injectors then adding the sensors until the fault returned.
I don't know what year of model your vehicle is but the later models power steering is not connected up. The sensor is there and part of the wiring harness at the sensor end is present, however if you follow the wiring it disappears into the engine harness, but the connector pins at the ECM end are empty?

Last edited by Lovel; 15th May 2017 at 08:13..
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Old 15th May 2017, 17:56   #7
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It's a 2004 1.8 SE and just about any possible option wiring that could be left out was. However this was definitely connected both ends and isn't just a switch, it's a three wire sensor. It was pulling the sensor power line down and messing up every other sensor on the engine, it was just the coolant temp that was obvious, the rest showed up when trying to drive it.
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Old 15th May 2017, 20:08   #8
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Quote:
Originally Posted by Geoff130 View Post
It's a 2004 1.8 SE and just about any possible option wiring that could be left out was. However this was definitely connected both ends and isn't just a switch, it's a three wire sensor. It was pulling the sensor power line down and messing up every other sensor on the engine, it was just the coolant temp that was obvious, the rest showed up when trying to drive it.
Hmm strange. I have traced the wiring on two 1.8T facelift models and found no wiring at the ECM connector although the power steering sensor wires and sensor were still present. Perhaps difference between turbo and nasp models?
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Old 15th May 2017, 20:29   #9
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You're probably right, if any car needs a bit more throttle when the steering is on full load the 1.8 nasp is the one. I wish mine had never been connected,it's currently unplugged and judging by the online prices for a new one it might stay that way for a while.
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Old 16th May 2017, 09:08   #10
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Quote:
Originally Posted by Geoff130 View Post
I found it by removing every pin on the large ECU connector apart from IGN, coolant temperature sensor, coils and injectors then adding the sensors until the fault returned.

Excellent fault-finding technique Geoff, although a painstaking one by the sound of it.

Simon
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