The car is a 1998 SEAT 2.0 Itr petrol Toledo, the issue is that occasionally the gearbox seemed to slip and twice went into default 3rd gear and would not change until the ignition was cycled. The slipping was not specific to any one gear but happened most often after decelerating into a bend. This instruction were recorded using the car diagnostic tool VCDS to test auto transmission.
If you want to know more about VCDS function, please refer to VCDS cases.
Preparation:
How to Configure VCDS & Diagnostic Cable for Your Laptop
VCDS 17.8.1 Full+Loader V2/V4 Free Download
Procedures:
Connect vehicle OBD port to laptop by VAG-COM with HEX-USB+CAN interface, running software
Click “02-Auto Trans”
After a few seconds VAG-COM has identified the gearbox control system fitted to the car and displays the information above.
The VAG number is the VAG part number for the ECU
The component field shows the system type
The soft coding shows the configuration
The Shop# shows the ID for the dealer who worked on system last
Click “Fault Codes -02”
After a second or two we get the fault codes back from the control unit
00266 – Solenoid Valve 5(N92) 31-10 – Open or Short to Ground – Intermittent
Notice VAG-COM also tells us the fault is not currently present but has been recorded as intermittent
Click “Save Codes” to save record of the code
Click “OK”, then go back to the main auto transmission screen
Click “Meas. Blocks – 08”
The numbered groups show live data coming from the gearbox controller.
Group 1 lists selector lever, throttle valve voltage, the position of the throttle as a percentage of fully open and shows the outputs from the multifunction switch.
Other groups show throttle position, gear selection, solenoid voltages, solenoid current flow, multifunction switch outputs and a whole lot more.
Skiped to group 4 which shows the current selected gear together with the road speed and active solenoids.
Solenoids 1,2,3 and 4 control the active gear, while solenoid 6 controls the torque converter lock-up clutch
The driving mode(or gear selected) shows us the car is in 2nd gear and the drive is hydraulic(notice solenoid 6 is off, so the torque converter lock-up clutch is not applied)
Now the car is in 4th gear mechanical. Notice solenoid 6 is active so the torque converter is locked and we have mechanical drive right through the gearbox
This is 3rd gear mechanical. You can see the only active solenoid is the converter lock-up. If all the electronics on the gearbox were to fail we’d still have 3rd gear, but lost the lock-up. This would be the “limp home” or default mode.
Solenoid 5(the one mentioned in the fault code) controls the pressure during each gear change so is not related to one particular gear. On a road test is can be seen to briefly pulse as the gearbox changes gear.
Go back to main auto trans screen.
Since the fault on this car indicates a solenoid inside the gearbox, we’d have to drop the sump to test it, so before doing that we would run continuity tests from the TCM(transmission control module) and check for a good resistance throught the circuit while wiggling the wiring harness and connections.
Luckily on this car(and apparently quite common) the fault was only the multi connector going into the top of the gearbox which was loose.After checking it for cleanliness and tightening it up the fault did not re-occur.
More repair cases about Seat, please refer to SEAT TROUBLE REPAIR.