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CVT diagnosis

CVT diagnosis 1
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CVT diagnosis

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Returning to the topic of repair of variator transmissions in previous articles, it became necessary to raise the priority question – DIAGNOSTICS.

It should be noted that most users of machines with such transmissions are not ready to make the right decision in case of problems. Most car services, including dealerships, are not ready for this either. As practice has shown, in most cases everyone rushes to disassemble it. This is a gross mistake – to disassemble the mechanical part of the unit when the CHECK banner is on – clearly indicating the presence of an electronic malfunction. Worse, such an operation in most cases does not lead to finding a true malfunction. Moreover, to the existing malfunction are added newly introduced during inept assembly – disassembly. Apart from the money spent – we can say that there is nothing to help here. Diagnosis is no longer possible. Rather, it can be done using a tester and a visual inspection – but this is more like a diagnosis of an injection engine, which lies separately from the machine on a pallet. Therefore – repeating – all that can be done – it is possible and necessary on the machine, when something else is connected and working.

Not everyone has a CONSULT dealer scanner, but those who, by definition (dealers), cannot always use it.

1. NISSAN BLUEBIRD (RE060FA) 99 years old, CVT is on, CONSULT is connected at the dealership – they report: there are no errors, everything is fine. The owner asks us to drive specialists – the car really does not drive, but there are no mistakes – we can’t do it. The malfunction appeared after warming up the box – transition to emergency mode.
Options are offered – from simple – changing the oil, replacing all the sensors in a circle, replacing the box with a new one. A fairly wide range of services, some offer only to check the oil level and change the oil, or a new transmission. The price of the issue is from 8,000 USD (with a car cost of up to 10,000 USD. Few dare.)

2. NISSAN MICRA 2000. NCVT. The CVT lamp flashes in motion and the car (its box goes into emergency mode) Okay –BLUEBIRD was right-hand drive (although the transmission is not linked to the steering wheel position). Here dealers replaced oil, candles, all filters, washed the injector – in general, a lot of work, but the error remained. According to the owner – he was rolled (test drive), showing on the scanner some incorrect data issued by the faulty CVT. Summary – Replacement CVT.
A malfunction occurred in the movement after warming up – when the car tried to pick up speed above 30 km / h, it twitched .

When people come to you with such malfunctions, and even with a printed list of work and diagnostic procedures from dealers, you immediately have doubts – is it worth it to take on repairs if there is already so much redone, but there is no result? Where to start? In any case, with an external examination – what was done and how. In such cases, it is advisable to check the connectors for their correct connection, as well as the cleanliness of the electrical contacts. After an external inspection, checking the oil level and its purity, you can try to start the self-diagnosis procedure, which all NISSAN electronic transmissions have. the procedure itself is very similar to a similar operation on a stepped automatic transmission, but there are differences. Naturally, the codes are different. Many nodes are checked similarly to automatic transmission (Park N switch), position check and adjustment are similar to automatic transmission, HPS – operation noise when opening the damper, etc..

First of all, you need to make sure that the TPS is installed correctly (it was not twisted and it is working). To do this, it is desirable to have a scanner that reads at least DATA STREAM from the motor. Today – the most overwhelming scanners do it.

It is necessary to check – the level of the TPS signal, as well as the status of the IDL signal .
TPS – 0.4 v – 0.5 v, IDL – closed (ON) .

Without an IDL signal, self-diagnosis may not start. !!

The IDL signal can be generated by a separate IDL –FULL THROTTLE contact group (6-pin TPS, for example RB25, SR20 motors), as well as three contact TPS at the level of 0.4 volts. (motors GA, GC). You can check the level with a tester. You can remove the brown chip with the engine running – the RPM of the twentieth should fall by no more than 100, reconnected – the XX should remain normal. If not, check the TPS, or teach the ECU level XX. (Idle volume learning)

On some recent models (for example SERENA with SR20DE), there may be a start-up assist system, which is implemented as a spring-loaded stem, which opens the throttle to a small angle. On the other hand, this rod is connected to a vacuum servo motor, the vacuum for which is taken from behind the throttle space. In other words, if the motor is shut off, the shutter is ajar and the IDL contact is open. Self-diagnosis can not be done. After starting, the discharge through the diaphragm retracts the rod, and the damper rises on its own stop body. In such a system, it is necessary either to remove this actuator, or by applying a vacuum from a manual pressure gauge, release the valve stroke so that the IDL contact closes. The damper must abut against its closed position limiter..

Before diagnosis, the engine and transmission must be warmed up in motion. Some manuals require connecting CONSULT and checking the temperature sensor in the automatic transmission – the voltage should be less than 0.9 Volt. In fact, it looks like this – the car should drive several kilometers before arriving at you.

Procedure for self-diagnosis.
1. the machine warmed up in motion
2. all consumers are switched off, like headlights, glass heating, air conditioning, etc.
3. the battery is working, voltage is more than 12 volts
4. There are no alarms breaking regular chains.
5. gear selector in position P

1. insert the key into the lock, turn from the off (OFF) position to the on position (ON) – when the indicator lamps on the instrument panel light up (the next position is the start, OFF is the ACC position) do this twice (OFF – ON, OFF – ON – OFF) leave it off (do it quickly)

2. gear selector in position P – turn the ignition on, wait for the CVT (SPORT) lamp to light for two seconds, immediately turn off the ignition (OFF)

3. depress the brake pedal and shift the gear selector to position D

4. turn on the ignition ON

5. release the brake pedal and move the selector to L

6. simultaneously fully depress the brake and gas pedals and without releasing them move the selector to D

7. release both pedals

First there is a start pulse of 2 seconds (similarly when the ignition is turned on – if everything is working properly), then the lamp will flash 10 times, and one should look at the flashes. They will be all short – half a second, but some will be long (about a second). The long flash number from the start of the series of 10 is the error number .
error example 3 and 8 (conditionally I short flashes, O – long)
I I O I I I I O I I I I I I I I
read the error code

Self-diagnosis error codes
2 second start – then all pulses are short (10) – no errors

1 pulse longer than the rest (P0720) auto speed sensor (secondary speed sensor) .
2 pulses longer than the rest (P0715) – primary speed sensor (drive shaft)
3 TPS (P1705)
4 STEP MOTOR (P1777) – open circuit – winding short circuit
5 CVT pressure sensor (P1791)
6 HPS linear pressure solenoid (P0745)
7 Lock UP GT Lock Solenoid (P0740)
8 CVT oil temperature sensor (P0710)
9 No engine speed signal (P0725)
10 when one code appears 10 – replace the ECU, if paired with others, first eliminate the low-order codes .

Suppose that for some reason the self-diagnosis procedure did not start. If the box is constantly in emergency mode, first you need to check the health of the STEP MOTOR windings on the connector in the box (under the battery) Resistance and numbering are in previous articles.

Actually, through this connector you can check all the internal electronic components of the box (to replace which you will have to drain the oil and remove the pan, filter)
If the malfunction is more complex, it manifests itself in motion and not always – then such measurements must already be done with external speed sensors and already in motion. To do this, you will have to find the ECU CVT unit. It starts with the numbers 31036 – XXXXX .

On cars – usually located in the center of the dashboard under the tape recorder (you have to disassemble everything), on minivans (such as SERENA) – you should look for it under the glove box on the passenger side, closer to the left strut.

There are two connectors on the block, view from the side of the block contacts:

The outputs of the sensors of the primary shaft Pin 38 and the secondary pin 29 are checked by the oscilloscope in motion. Waveform – meander, amplitude 10-12 volts.

TPS IDL pin 16, FULL pin 17, pressure sensor pin 37

If the car is constantly driving in emergency mode, both cold and hot, the STEP MOTOR _ winding breakage is most likely to fail. The malfunction arising after warming up is rotation sensors. In this case, you need to disassemble everything (for access to the ECU) and send the owner to test drive. Be sure – 10 minutes of active driving is enough for him. As soon as the car pulls up in emergency mode – connect the device and watch the signals .

If the CVT stalls, check the port pressure and voltage at the pressure transducer in stall test mode. This will say a lot about the condition of the box..

Since the writing of the previous article, information has appeared about the availability of a V-belt (chain) for this type of transmission. The declared price for the new chain is 12,000 rubles. In principle, in the presence of such an unreliable element (to mileage over 150,000 km), repair of the box is real .

In order not to ride on the “powder keg” – that’s exactly what most owners of used cars with critical mileage drive (long trips are contraindicated for them), and also not to read horrific stories about the sudden death of the variator in the middle of the uninhabited Arctic snows, it probably makes sense change it in advance, at the first TO car, so as not to spoil your summer vacation with your family on a long journey. This is better than buying a used variator in an unknown state for 1500USD without warranty on mileage.

For examples, BLUEBIRD – self-test did not start (QG18DDNeo Di) motor.
Electronic shutter – perhaps because of this. When the ignition is turned on, the flap is moved to the start position by the servomotor and IDL disappears. There is nothing you can do with the shutter, all modes and level XX are set by its position. The oscilloscope detected a signal loss from the secondary speed sensor after warming up. After replacing the sensor – the defect is gone.

With NISSAN MICRA (MARCH) with a liter engine – the problem turned out to be not in NCVT at all, but in TPS (3 pin), there was no IDL signal, XX 1500 (no tachometer)

TPS is not diagnosed by self-diagnosis (only the level in the datastream) there is no direct error code. The dealers’ mistake is obviously the first thing they did when they looked at the engine errors – they weren’t found, and the DPS did not check for DATA STREAM. So it was concluded that CVT was malfunctioning (although on this model it can be said hydraulic). The TPS was almost 3 volts, at the beginning of the movement there was a blockage of the electropowder GT (with this opening of the damper by TPS) there was a blow to the transmission and a transition to emergency mode. Replacing TPS and adjusting returned XX to the proper level, and NCVT to working condition.

It is advisable for fans to drive a car with CVT to put an additional oil cooler in the cooling circuit, as is done on the HYPER CVT M6 .
The temperature there is very high, there is a spray bottle inside the box that supplies oil to cool the circuit. The radiator can be taken from any jeep (small size from the engine oil cooling system or automatic transmission). The resource of the box will increase significantly! Failure of STEP MOTOR, as a rule, occurred after arrival in the summer along the highway at a speed of 140 km / h for an hour. After a stop – the car stopped driving. Increased heating of the oil led to a break in the winding .

The so-called “interservice” oil change interval is also desirable to reduce. In addition, the trend of modern automakers in view of modern competition and dishonest marketing leads to excessive overestimation of the time for oil change, as an advertising slogan to reduce the cost of maintaining the car.
All this is beautiful, while it is new and under warranty. Many and the warranty period with difficulty “reach.” And after the guarantee – everything falls apart.

For example : Peugeot dealer in Moscow set an oil change date of 30,000 km. And candles too. After the second oil change – the engine hardly survives to the third – then overhaul, or oil consumption exceeds gasoline consumption. Well, to leave 30,000 km on our gasoline – no candles can stand it. Here they are cleaned in the 21st century with a sandblasting machine..

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