My Nexon done 11,000 km starts knocking: Tata ASC has no clear solution

Many follow ups and visits to the service center, now they claim the ECU is gone because of a bad signal from the acceleration sensor

BHPian dr.dre recently shared his with other enthusiasts.

I never imagined I would be writing this thread 🙁

Had been on a Bangalore to Mangalore return trip early December 2022, driving my Nexon BS4 D AMT which has run 11+k on odo, thanks to COVID and other cars in family, it has seen limited usage.

The car started to jerk and knock, aggravating when i take the foot off the accelerator. It’s more prominent post gear change in higher gears. I moved the stick to manual mode at times and got it back home to Bangalore, as gently as I could.

The engine at idle is stable, used neutral as and when required to gain composure.

The car is just out of extended warranty, and always serviced at Key Motors, Mysore Road. So took it to them and the horror story starts.

They drove the car and said it may need an injector cleaning, they will check and let know. Few days go by and am told they want to check the injection pressure and will send it to an external vendor. If a fault is detected, a overhaul or calibration may cost like 50k.

I followed up again, they said it did not resolve the issue and want to check the fuel pressure pump, they claim to have overhauled and recalibrated all of it and unfortunately it did not resolve the issue. Many follow ups and visit to service center, now they claim the ECU is gone because of bad signal from the acceleration sensor

Their lame explanation is driving me furious, as they are clearly not able to figure out the issue. How can a car run for 11k have a ECU failure, Fuel Pump Damaged, Injector’s blocked or out of calibration all at once.

Is there anyway I can salvage and rescue the car now.

What could really be the issue here? Is there a way I can get help from TATA?

Appreciate your valuable suggestions or leads on this, thank you.

Here’s what BHPian SS-Traveller had to say on the matter:

In warranty, Tata would have happily replaced the whole engine, gearbox, ECM as well as the axles, wheels and tyres in their effort to sort out the problem. Out of warranty, they’ll make you pay for all of it.

First thing to do: Take it to a competent FNG. I’m sure there are plenty in Bangalore. Start the troubleshooting with the basics. Listen to the engine. Is there any weird knocking sound at idle? Can the engine be freely revved in neutral without knocking or choking? Is the exhaust note sounding right?

Is the fuel supply fine? Clean the tank and fuel lines, check the low pressure pump, change the diesel filter. Check with an OBD2 scanning tool for any DTC (diagnostic trouble codes) even though the check engine light (CEL) is not glowing. If there are stored error codes, check what they say, and try to sort out the issues causing them. An ECM failure is certain to throw a CEL. There are plenty of ECM repairers in our big cities – changing the ECM is not necessary in most cases.

Are the gears shifting fine? Jack up the driving wheels and chock the rear wheels (safety first) and check if the gears are shifting as expected in both manual and automatic mode. Does the gearbox control module show any error code?

If that does not resolve the issue, it would be time to address the high pressure pump, the common rail and the injectors. You need specialist help here. Find out which company makes the common rail diesel injection system fitted to your car – IIRC it is Bosch. Look up your local Bosch Diesel Service centre, and ask them to calibrate the high pressure pump and test & clean the injectors. Check the compression in each cylinder when the injectors are out.

Hope your issue gets resolved soon.

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