P1812 , P1813
Symptom: Disturbances in lock-up and gear-shifting functions at higher temperatures.
Transmission fluid temperature sensor, shorted to ground (P1812), or open circuit or shorted to B+ (P1813).
Fault symptoms
Disturbances in lock-up and gear-shifting functions at higher temperatures.
Conditions
P1812:
Shorting to ground.
P1813:
Shorting to battery voltage or open circuit and if the control module reads a fluid temperature lower than -10°C when the engine has been running for about 5 minutes.
Diagnostic help
Current fluid temperature can be read with the diagnostic tool. Select "READ FUNCTIONS". Select "FLUID TEMPERATURE". With warm engine and gearbox, the nominal fluid temperature will be approx. 80C and approx. 1.1 V.
Check the wiring
Intermittent faults may occur as a result of temporary short circuits and breaks in the wiring. Jiggle the leads at several places and in different directions to reveal any faults in the wiring harness, including connectors. Observe the multimeter, test lamp or ISAT scan tool while carrying out this check.
Diagnostic procedure
1 Check the fluid temeprature sensor's connection to ground
Unplug connector H16-3 (16-pin connector located behind the battery) and connect a test lamp to pin 12 of the female connector and battery positive (B+).
Is the lamp alight?
Continue with step 2.
Repair or replace the wiring (including connectors) between connector H16-3, pin 12 of the female connector, and grounding point G4.
2 Check the transmission control module's signal input
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Connect the diagnostic tool.
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Turn the ignition to the ON position.
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Select "READ FUNCTIONS".
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Select "FLUID TEMPERATURE".
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With pin 12 open, the diagnostic tool should read less than -40C.
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With pin 4 and pin 12 coupled together, the diagnostic tool will show more than 175C.
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Are both readings OK?
Continue with step 3.
Continue with point 4.
3 Check the wiring
Check the continuity of the wiring between • pin 4 of connector H16-3 and the temperature sensor's connector (the pin marked 20). • pin 12 of connector H16-3 and the temperature sensor's connector (the unmarked pin).
Is the wiring OK?
Change the temperature sensor and proceed to point 5.
Rectify the fault and continue with point 5.
4 Check the wiring connected to the transmission control module
Check the continuity of the wiring between pin 4 of female connector H16-3 and pin 33 of the transmission control module.
Is the wiring OK?
Continue with point 5.
Rectify the fault and continue with point 5.
5 Final check
Clear the diagnostic trouble code, drive the car on test at varying engine loads and speeds for 5 minutes and obtain readouts of any diagnostic trouble codes that are generated.
Does the diagnostic trouble code recur?
Continue with
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The remedial action taken was correct.
