Electronic transmissions and scan tools

Using the workshop manual we can identify all of the sensors and actuators related to the Power train control module.

Below is a picture of the wiring diagram of a power train control module and their related sensors and actuators.

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By using the chart above we can make the following statements:

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-Shift solenoid 1-2 and 2-3 are on when the vehicle is shifted into drive & starts out in first gear.

-Only shift solenoid 2-3 is on when the vehicle automatically shifts into second gear.

-There are no solenoids on when the vehicle automatically shifts into third.

-Only shift solenoid 1-2 is on when vehicle automatically shifts into fourth
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In case of a solenoid malfunction and none of the solenoids can be actuated ,the vehicle can go into 3rd gear and still just drivable so the vehicle can be taken to a garage or a place to be looked at ... the manufacturer decides this by looking at the performance of the engine and which gear would give us enough speed and at the same time enough torque to allow the car to start from the stationary state and at the same time enough speed so the car can be driven on the road or highway if necessary with out causing too much danger to the occupants and other drivers so this gear can change from a car with low performance engine might be 2nd gear and some other cars with a higher performance engine to have this default gear placed on the 3rd or in some cases even 4th gear.

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Fault codes:

code: 58 Transmission Fluid temperature (TFT) , signal voltage low. Check power train lamp not illuminated .

For testing the ECT sensor ... we can pull the sensor out and test it on a bench and put it in some water and heat the water up to see if the resistance of the sensor changes correctly (they are normaly NTC so the resistance drops as the temperature increase) and also to check the manufacturer specification for the parameters of this sensor to make sure it is working in the correct range.

Also we can check the circuit by checking for voltage drops on the signal wire to see if there are any high resistance in the signal wire, we can also check the signal voltage against the manufacturer spec to see if we are getting the right voltage or to voltage drop the ground and checking to see if the ground side of the circuit doesn't have any high resistance ... we do this by putting negative prob of the voltmeter on a good ground eg . negative post of the battery and other prob on the earth side of the circuit to see if there is significant voltage difference between the two points . In the manufacturer manual states this code can also be the cause of the transmission fluid temperature reaching 182 degree C for 1 second . but there are no default actions taken by the Power train control module.

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Code: 82 , 1-2 shift solenoid circuit faulty. Check power train lamp is illuminated .

In order for us to get this fault code the PCM has detected an in appropiate voltage on the 1-2 shift solenoid cuircuit for 2 seconds or longer. This will cause the shifts to be firm hard shifts and this is because all the set line pressure is pushed to the maximum . It also could cause the power train to only go in to the 2nd and 3rd or only 1st and 4th. The torque converter clutch also would not be actuted on so it can help with smoothing the ride and having more torque if needed . We can check the supply voltage and because they are normally earth triggered with the ignition on we should have supply voltage to the solenoids which we can check against manufaturer spec , we can also locate a high resistance or open curcuit before the solenoide... an other way we can check this solenoid is to check the earth side of the circuit but pay attention to the situation where we are checking the solenoid and whether it is supposed to be on or not at time of checking ... we can voltage drop the earth to see if the solenoid has good earth or any high resistance or bad connections on the earth circuit . At last and not least we can take the solenoid out and test it on a bench eg. resistance of the winding or to see if there is any earth leaks to the body and even by knowing the voltage from the manufaturer spec we can test the solenoid and not damaging it to see if it is working appropiatly or infact faulty which replacement is an easy option since we have already removed it .

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Torque converter clutch:

Unfortunatly we couldnt see the Torque converter clutch on our live data on the scan tool so I cant say when exactly it is on or off but from the what I've learned so far can tell you that the torque converter lock up clutch only comes on when the vehicle is in cruise mode and does this to conserve energy when cruising by locking up the torque converter and is disengaged usually by the foot brake pedal switch or when the speed of the vehicle has decreased past and less than the speed set by the manufacturer.

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