Function
To inform the throttle control unit the position of the two throttle valves and to drive them both.
Operating principle
All the unit internal components (potentiometer and electric motor) are contactless; therefore, no electrical diagnosis is possible for the throttle body, only for the circuits connected to it.
Throttle body activation takes place every time the key is set to ON: correct activation is indicated when the stop lights turn on.
If during activation, the engine is started, the activation is not completed and the stop lights do not turn on.
Every 150 key-ONs, however, the throttle valves are forced to activation. If start-up is attempted during this activation (which requires 3 seconds), the engine will not start.
Level in wiring diagram: throttle control unit.
Location:
- on the vehicle: inside the filter casing
- connector: on the throttle body
Pin-out:
1. potentiometer signal: 1; 2. supply voltage + 5V; 3. throttle valve control (+); 4. potentiometer signal: 2; 5. throttle valve control (+); 6. ground connection
Caution! Before carrying out any troubleshooting, carefully read the general troubleshooting concepts for electrical devices at the beginning of the check and control section in the electrical system chapter.
Axone: parameters
Front throttle Potentiometer 1 (voltage)
- Example value: 800 mV
The value in the example refers to engine conditions with key set to ON.
Front throttle Potentiometer 2 (voltage)
- Example value: 3878 mV
The value in the example refers to engine conditions with key set to ON.
Rear throttle Potentiometer 1 (voltage)
- Example value: 780 mV
The value in the example refers to engine conditions with key set to ON.
Rear throttle Potentiometer 2 (voltage)
- Example value: 3756 mV
The value in the example refers to engine conditions with key set to ON.
Front throttle Potentiometer 1-2 (degrees) / Rear throttle Potentiometer 1-2 (degrees) Example value: 6.5°
With key set to ON, the throttle is kept in position by the springs (approximately 5-7°). After the engine starts up at idle, the throttle is kept close to the mechanical minimum (above or equal to 0.5°). When the gear is not engaged, at approx. 6000 rpm, throttles open very little because the requested torque is too low (approximately 5-7°).
Front / rear cylinder throttle correction
- Example value: 0.0°
For example, if there is a hole in the intake manifold, the pressure read is different from the pressure estimated by the control unit and the system tries to reach an "estimated" situation by opening the throttle a little bit more; therefore, this parameter takes a value different from zero: an acceptable value should be between -0.7° and +0.7°.
Front cylinder Limp home position / Rear cylinder Limp home position
- Example value: 800 mV / 780 mV
Voltage stored in the control unit corresponding to the throttle Limp home position.
Front throttle lower position / Rear throttle lower position
- Example value: 502 mV / 492 mV
Voltage stored in the control unit corresponding to the throttle mechanical minimum position.
Axone: statuses
Throttle Self-learning
Example value: carried out/not carried out
Indicates whether or not the autodetection process has been carried out through the diagnosis instrument.
Axone: electrical errors
Potentiometer 1 sensor, front throttle position P0120
Example value: short circuit to positive/ open circuit, short circuit to negative
Error cause
If shorted to positive: excessive voltage has been detected at PIN A6 of the throttle control unit. If the circuit is open, shorted to negative: voltage equal to zero has been detected at PIN A6 of the throttle control unit.
Troubleshooting
if shorted to positive: check the value shown by the parameter of the front throttle Potentiometer 1 (voltage): disconnect the left connector and see the value displayed by Axone: if the voltage does not vary, there is a short circuit in the cable wiring; replace the throttle body if the voltage drops to zero.
if the circuit is open, short circuit to negative: check the throttle body connector and the throttle valve connector. If not OK, restore; if everything is OK, check circuit continuity between the two terminals. If not OK, restore the cable harness; if OK, check the circuit earth insulation (from throttle sensor connector or control unit connector). If it is earth insulated, check that there is power (+5 V) at the throttle body connector PIN 2, and that PIN 6 is connected to ground. If both are correct, replace the throttle body.
Potentiometer 2 sensor, front throttle position P0122
Example value: short circuit to positive/ open circuit, short circuit to negative Error cause
If shorted to positive: excessive voltage has been detected at PIN A5 of the throttle control unit. If the circuit is open, shorted to negative: voltage equal to zero has been detected at PIN A5 of the throttle control unit.
Troubleshooting
if shorted to positive: check the value shown by the parameter of the front throttle Potentiometer 2 (voltage): disconnect the left connector and see the value displayed by Axone: if the voltage does not vary, there is a short circuit in the cable wiring; replace the throttle body if the voltage drops to zero.
if the circuit is open, short circuit to negative: check the throttle body connector and the throttle valve connector. If not OK, restore; if everything is OK, check circuit continuity between the two terminals. If not OK, restore the cable harness; if OK, check the circuit earth insulation (from throttle sensor connector or control unit connector). If it is earth insulated, check that there is power (+5 V) at the throttle body connector PIN 2, and that PIN 6 is connected to ground. If both are correct, replace the throttle body.
Potentiometer 1 sensor, rear throttle position P0125
Example value: short circuit to positive/ open circuit, short circuit to negative
Error cause
If shorted to positive: excessive voltage has been detected at PIN B6 of the throttle control unit. If the circuit is open, shorted to negative: voltage equal to zero has been detected at PIN B6 of the throttle control unit.
Troubleshooting
if shorted to positive: check the value shown by the parameter of the Front throttle Potentiometer 1 (voltage): disconnect the left connector and see the value displayed by Axone: if the voltage does not vary, there is a short circuit in the cable wiring; replace the throttle body if the voltage drops to zero.
if the circuit is open, short circuit to negative: check the throttle body connector and the throttle valve connector. If not OK, restore; if everything is OK, check circuit continuity between the two terminals. If not OK, restore the cable harness; if OK, check the circuit earth insulation (from throttle sensor connector or control unit connector). If it is earth insulated, check that there is power (+5 V) at the throttle body connector PIN 2, and that PIN 6 is connected to ground. If both are correct, replace the throttle body.
Potentiometer 2 sensor, rear throttle position P0127
Example value: short circuit to positive/ open circuit, short circuit to negative Error cause
If shorted to positive: excessive voltage has been detected at PIN B5 of the throttle control unit. If the circuit is open, shorted to negative: voltage equal to zero has been detected at PIN B5 of the throttle control unit.
Troubleshooting
if shorted to positive: check the value shown by the parameter of the Rear throttle Potentiometer 2 (voltage): disconnect the left connector and see the value displayed by Axone: if the voltage does not vary, there is a short circuit in the cable wiring; replace the throttle body if the voltage drops to zero.
if the circuit is open, short circuit to negative: check the throttle body connector and the throttle valve connector. If not OK, restore; if everything is OK, check circuit continuity between the two terminals. If not OK, restore the cable harness; if OK, check the circuit earth insulation (from throttle sensor connector or control unit connector). If it is earth insulated, check that there is power (+5 V) at the throttle body connector PIN 2, and that PIN 6 is connected to ground. If both are correct, replace the throttle body.
Front throttle supply voltage during self-learning P0164
Example value: low supply voltage
Error cause
The throttle power supply is too low to carry out the autodetection test correctly (at each key ON). The instrument panel does not indicate the presence of this error even in the ATT status.
Troubleshooting
The throttle test is not carried out when the key is set to ON because the test could show unreal errors (because the voltage is too low). Voltage is detected by the Marelli control unit.
Front throttle control circuit P0166
Example value: short circuit to positive / short circuit to negative / open circuit, overcurrent, excessive internal temperature.
Error cause
If shorted to positive: excessive voltage has been detected at PIN C1 of the throttle control unit connector. If shorted to negative: no voltage has been detected. If the circuit is open: an interruption has been detected.
Troubleshooting
if shorted to positive: disconnect the throttle body connector, set key to ON and check voltage at PIN 3: if the voltage read is higher or equal to 5V, there is a short circuit on the cable harness; replace the throttle body if the voltage is null
if shorted to negative: disconnect the throttle body connector, set the key to ON and check if PIN 3 is in continuity with the vehicle ground connection: if it is, there is a short circuit in the cable ground connection; if it is not, replace the throttle body.
open circuit, overcurrent, excessive inside temperature: check the throttle body connector and the throttle control unit connector. If not OK, restore. If everything is OK, disconnect the throttle body connector (PIN 3) and the throttle control unit connector (C1) and check the circuit continuity between the two terminals; if there is no continuity, restore the cable harness. If there is continuity, with the throttle body connector connected, check that the resistance, from the throttle control unit connector, between PIN A1 and C1 is within 1 and 2.5 Ohm; if it is not, replace the throttle body; if it is, check that the throttle body is not mechanically blocked: if blocked, solve the problem and replace the body; if it is not, replace the throttle control unit.
Rear throttle supply voltage during self-learning P0184
Example value: low supply voltage
Error cause
The throttle power supply is too low to carry out the autodetection test correctly (at each key ON). The instrument panel does not indicate the presence of this error even in the ATT status.
Troubleshooting
The throttle test is not carried out when the key is set to ON because the test could show unreal errors (because the voltage is too low). Voltage is detected by the Marelli control unit.
Rear throttle control circuit P0186
Example value: short circuit to positive / short circuit to negative / open circuit, overcurrent, excessive internal temperature.
Error cause
If shorted to positive: excessive voltage has been detected at PIN 8A of the throttle control unit connector. If shorted to negative: no voltage has been detected. If the circuit is open, there is overvoltage or excessive internal temperature: an interruption or excessive ampere input or control unit overheating has been detected.
Troubleshooting
if shorted to positive: disconnect the throttle body connector, set key to ON and check voltage at PIN 3: if the voltage read is higher or equal to 5V, there is a short circuit on the cable harness; replace the throttle body if the voltage is null.
if shorted to negative: disconnect the throttle body connector, set the key to ON and check if PIN 3 is in continuity with the vehicle ground connection: if it is, there is a short circuit in the cable ground connection; if it is not, replace the throttle body.
open circuit, overvoltage, excessive inside temperature: check the throttle body connector and the throttle control unit connector. If not OK, restore. If everything is OK, disconnect the throttle body connector (PIN 3) and the throttle control unit connector (C8) and check the circuit continuity between the two terminals; if there is no continuity, restore the cable harness. If there is continuity, with the throttle body connector connected, check that the resistance, from the throttle control unit connector, between PIN A8 and C8 is within 1 and 2.5 Ohm; if it is not, replace the throttle body; if it is, check that the throttle body is not mechanically blocked: if blocked, solve the problem and replace the body; if it is not, replace the throttle control unit.
Axone: logic errors
Potentiometer 1 sensor, front throttle position P0121 - signal not valid.
Error cause
Signal not within the expected value drawn according to the values of the intake pressure. Troubleshooting
Check the parameter of the Potentiometer 1 Front throttle (voltage) to get which signal the control unit receives and to compare it to the Potentiometer 1 Rear throttle (voltage). Check the throttle body connector as well as the throttle control unit connector. Check that cable resistance between the throttle body connector (PIN 1) and the throttle control unit (PIN 6A) is a few tenths of an Ohm. If this is not the case, restore the cable harness. If the value is correct, replace the complete throttle body.
Potentiometer 2 sensor, front throttle position P0123 - signal not valid.
Error cause
Signal not within the expected value drawn according to the values of the intake pressure.
Troubleshooting
Check the parameter of the Potentiometer 1 Front throttle (voltage) to get which signal the control unit receives and to compare it to the Potentiometer 2 Rear throttle (voltage). Check the throttle body connector as well as the throttle valve control unit connector. Check that cable resistance between the throttle body connector (PIN 4) and the throttle control unit (PIN 5A) is a few tenths of an Ohm. If this is not the case, restore the cable harness. If the value is correct, replace the complete throttle body.
Front throttle valve position sensors P0124 - illogical signal.
Error cause
Potentiometer 1 and potentiometer 2 do not show a logical value: the sum of the two voltages should be constant. The cause may be a malfunction in one of the two sensors or an abnormal resistance in one of the two circuits.
Troubleshooting
Check the throttle body connector as well as the throttle control unit connector. Check that cable resistance between the throttle body connector (PIN 1) and the throttle control unit (PIN 6A) is a few tenths of an Ohm. Check that cable resistance between the throttle body connector (PIN 4) and the throttle control unit (PIN 5A) is a few tenths of an Ohm. If one of the two is different, restore the cable harness. If correct, replace the complete throttle body.
Potentiometer 1 sensor, rear throttle position P0126 - signal not valid.
Error cause
Signal not within the expected value drawn according to the values of the intake pressure.
Troubleshooting
Check the parameter of the Potentiometer 1 Rear throttle (voltage) to get which signal the control unit receives and to compare it to the Potentiometer 1 Front throttle (voltage). Check the throttle body connector as well as the throttle control unit connector. Check that cable resistance between the throttle body connector (PIN 1) and the throttle control unit (PIN 6B) is a few tenths of an Ohm. If this is not the case, restore the cable harness. If the value is correct, replace the complete throttle body.
Potentiometer 2 sensor, rear throttle position P0128 - signal not valid.
Error cause
Signal not within the expected value drawn according to the values of the intake pressure.
Troubleshooting
Check the parameter of the Potentiometer 2 Rear throttle (voltage) to get which signal the control unit receives and to compare it to the Potentiometer 2 Front throttle (voltage). Check the throttle body connector as well as the throttle control unit connector. Check that cable resistance between the throttle body connector (PIN 4) and the throttle control unit (PIN 5B) is a few tenths of an Ohm. If this is not the case, restore the cable harness. If the value is correct, replace the complete throttle body.
Rear throttle position sensors P0129 - illogical signal.
Error cause
Potentiometer 1 and potentiometer 2 do not show a logical value: the sum of the two voltages should be constant. The cause may be a malfunction in one of the two sensors or an abnormal resistance in one of the two circuits.
Troubleshooting
Check the throttle body connector as well as the throttle control unit connector. Check that cable resistance between the throttle body connector (PIN 1) and the throttle control unit (PIN 6B) is a few tenths of an Ohm. Check that cable resistance between the throttle body connector (PIN 4) and the throttle control unit (PIN 5B) is a few tenths of an Ohm. If one of the two is different, restore the cable harness. If correct, replace the complete throttle body.
Front throttle Limp Home autodetection P0160 - test failed.
Error cause
Throttle position, kept by the springs, not within the expected range (at each key ON). The instrument panel does not indicate the presence of this error even in the ATT status.
Troubleshooting
Check if the throttle body and the intake duct are clean. If they are, replace the throttle body.
Front throttle mechanical springs autodetection P0161 - test failed.
Error cause
Return time of the throttle, kept in position by the springs, not within the expected limits: the causes can be a deterioration of the performance of the springs or excessive throttle friction (at each key ON).
Troubleshooting
Check if the throttle body and the intake duct are clean. If they are, replace the throttle body
Front throttle minimum mechanical position autodetection P0162 - test failed.
Error cause
Position of the throttle stop not within the expected range (at each key ON).
Troubleshooting
Check if the throttle body and the intake duct are clean. If they are, replace the throttle body.
Detection of front throttle valve Recovery conditions (air T°, water T°) P0163 - possible presence of ice.
Error cause
A correct throttle rotation cannot be detected given low ambient and engine temperatures: some ice may have formed in the duct (at each key ON). The instrument panel does not indicate the presence of this error even in the ATT status.
Troubleshooting
Check that the throttle body is clean and that there is no ice or condensation in the intake duct. If they are, replace the throttle body.
Front throttle first self-learning NOT performed P0165 - test not carried out.
Error cause
The first throttle self-learning process has not been successful or has not been carried out. The instrument panel does not indicate the presence of this error even in the ATT status.
Troubleshooting
Delete errors hindering throttle self-learning.
Front throttle position error P0167 - misalignment between control and activation.
Error cause
The throttle mechanical control may be damaged.
Troubleshooting
Replace the throttle body.
Rear throttle Limp Home autodetection P0180 - test failed.
Error cause
Throttle position, kept by the springs, not within the expected range (at each key ON). The instrument panel does not indicate the presence of this error even in the ATT status.
Troubleshooting
Check if the throttle body and the intake duct are clean. If they are, replace the throttle body.
Rear throttle mechanical spring autodetection P0181 - test failed.
Error cause
Return time of the throttle, kept in position by the springs, not within the expected limits: the
causes can be a deterioration of the performance of the springs or excessive throttle friction (at each key ON).
Troubleshooting
Check if the throttle body and the intake duct are clean. If they are, replace the throttle body.
Rear throttle minimum mechanical position autodetection P0182 - test failed.
Error cause
Position of the throttle stop not within the expected range (at each key ON).
Troubleshooting
Check if the throttle body and the intake duct are clean. If they are, replace the throttle body.
Detection of the rear throttle Recovery conditions (air T°, water T°) P0183 - possible presence of ice.
Error cause
A correct throttle rotation cannot be detected given low ambient and engine temperatures: some ice may have formed in the duct (at each key ON). The instrument panel does not indicate the presence of this error even in the ATT status.
Troubleshooting
Check that the throttle body is clean and that there is no ice or condensation in the intake duct. If they are, replace the throttle body.
Rear throttle first self-learning NOT performed P0185 - test not carried out.
Error cause
The first throttle self-learning process has not been successful or has not been carried out. The instrument panel does not indicate the presence of this error even in the ATT status.
Troubleshooting
Delete errors hindering throttle self-learning.
Rear throttle position error P0187 - misalignment between control and activation.
Error cause
The throttle mechanical control may be damaged.
Troubleshooting
Replace the throttle body.
Reset procedure
If the Marelli control unit or the throttle body is replaced, do not start the engine within the 3 seconds after the key is set to ON; during this time the control unit carries out the throttle self-learning process: then make sure that the throttle self-learning status reads: carried out. If the indication is "Not carried out", delete any possible errors present in the vehicle. Carry out Throttle self-learning process on the adjustable parameters screen page (screwdriver and hammer), and check again that the throttle selflearning status reads: carried out.