P1716 and P1718
Symptom: "CHECK ACS" warning lamp alight. If there is no sensor input signal, the ACS control module will calculate a default value on the basis of wheel speed and the gear that is engaged. No other fault symptoms.
P1716: Gearbox rpm, value incorrect P1718: Gearbox rpm, input incorrect
Fault symptom
"CHECK ACS" warning lamp alight. If there is no sensor input signal, the ACS control module will calculate a default value on the basis of wheel speed and the gear that is engaged. No other fault symptoms.
Condition
P1716: A gear is engaged and the clutch is in engagement. The input shaft speed does not coincide with engine rpm or the calculated substitute value.
P1718: Input shaft speed >8000 rpm.
Warning
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To activate GEARBOX RPM the car can be driven while on a car lift. Extreme caution should be exercised if this method is chosen. If only the front of the car is jacked up and supported on stands, always apply the handbrake and make sure that nobody is in front of the car or beside the front wheels while this test procedure is in progress.
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Diagnostic procedure
1 Check the resistance of the sensor
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Unplug the sensor's 2-pin connector (grey) located beside the clutch actuator unit.
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Take a resistance reading across pins 1 and 2 of the sensor's connector. Nominal resistance is 550 ± 55 ohms.
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Is the reading correct?
Continue with point 2.
Change the sensor and proceed to point 5.
2 Check the sensor's mounting
Remove the sensor and check that its tip is not soiled with metal swarf, etc.
Is the sensor OK?
Continue with point 3.
Clean the sensor and continue with point 3.
3 Check the grounding of the sensor
Connect a test lamp to B+ and pin 2 of the connector. The lamp should light up.
Did the lamp light up?
Continue with point 4.
Repair or replace the lead in question and proceed to point 5.
4 Check the sensor's control module input
Take a resistance reading across pins 1 and 2 of the connector. Nominal resistance is 1 Mohm.
Is the reading correct?
Continue with point 5.
Repair or replace the lead in question and proceed to point 5.
5 Final check
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Clear the diagnostic trouble code.
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Perform a drive cycle by driving the car at varying engine rpm and loads for 5 minutes.
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Check whether the diagnostic trouble code has recurred.
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Has the diagnostic trouble code recurred?
Continue as described in the section "Before replacing a control module", see
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The steps taken to rectify the fault were correct.
