Q1: I own a 2004 Toyota Unser.
When the vehicle slows down, it jerks. The brakes are all right and the Unser looks to be fine at cruising speeds.
But I have noticed a humming sound. Is it gearbox problem?
Unser Owner
Kuala Lumpur
For a manual gearbox, the most probable cause of jerking is your clutch disc is worn out.
For an automatic gearbox, it could have trouble downshifting or upshifting. This can be remedied initially by flushing the automatic transmission fluid (ATF) and to observe for any changes.
Other possible causes are bent or loose linkages in the propeller shaft system; or faulty sensors or actuators in engine management.
The humming sound could be coming from the gearbox or differential.
As stated earlier, change the gear oil and observe for any changes. If there is no change, the next item to check is for backlash or big clearance between the two gears. Worn-out possible wheel bearings is another possible cause.
Send your car to a reputable workshop for a thorough inspection.
Q2: I have a 2009 Myvi 1.3 with auto transmission.
Recently, a light in the meter cluster lit up, blinking with check engine light on.
The service centre said it found a “P1602 communication with A/T” error but could not trace the source of the defect.
Another workshop said the timing chain was giving way, while another claimed an ECU problem.
I don’t know who to believe now.
Myvi Owner
Batu Caves
There are even more possibilities.
Your car is already four years old.
Have you changed the auto transmission fluid?
Some errors in the transmission ECU is caused by mechanical or hydraulic problem.
The car’s wiring should be checked also. Sometimes there are broken wires caused by mouse bites especially if you have a cat in the garage which sleeps inside your engine compartment and drags food there.
If all the physical inspection shows nothing amiss, the ECU is the next thing to check but only the scan tool for the Myvi will be able to detect this trouble. Send the Myvi to the dealership to have that done.
In Toyota vehicles, a P1602 alert signifies “ECU BATT Malfunction”, so there is no harm in checking the car’s charging system as well.
Q3: I have a 14-year-old car. The air-conditioner was running quietly until three weeks ago when it began to make a gurgling sound.
The sound seems to be coming from in front and under the dashboard. It sounds as if there’s not enough air-cond gas but the cabin is still quite cold.
What’s causing the noise?
Peter Han
Malacca
If you suspect low gas, have it checked by an air-cond technician.
If gas is low, the pressure reading should be around 1.5 – 2.5 bar and around 14-16 bar if high.
If the manifold gauge shows the reading to be 14-16 bar, there is no gas deficiency.
As for the sound, please check your air-conditioning blower fan under the dashboard on the passenger side. The fan motor may have caught some foreign objects or the motor itself is already faulty and due for replacement.
If the air-conditioning compressor bearing is worn out, it would cause the unusual noise. This component is driven by one of the belts in the engine compartment.
