[icubyx]

Hi all. I am new to this forum and need some advice from you. I own a 2016 Tata Tiago XZA and it has run barely 10000km.
A while ago, on a road trip, my engine light came up suddenly after a stopover and remained so. I took the car to the service center who told me after checking with the laptop that it was temporary error and they reset it. The engine light went away for a few days after that. After a few days, it came back again while driving in a slow moving traffic jam and the car became jerky while accelerating. I was about to take it to the service center and it disappeared by itself.
After a few days, I saw the light turn on again. Again I took it to the service center where they told me that a sensor in the hood needed to be replaced. After replacement, and resetting the codes, it went off for a few km and turned on again. Again a trip to the service center and after a diagnostic test, they told me that the ECU and the wiring needs to be replaced as the ECU has been damaged due to some fault in wiring. But I wasn't convinced. So I took the car back and told them I would do it later if it wasn't urgent.
After a few days of driving the car, the engine light went away by itself for about 500 km and now it is back again.
Can anybody tell me whether the ECU and wiring really needs to be replaced in this condition or does the cause lie somewhere else? it is an expensive repair estimated to cost around 60K.
Thank you!

[GTO]

Sounds like a very incompetent workshop to me. They're clearly throwing things at the wall, in the hope that something sticks. The check engine light could be due to a wide number of factors. I suggest you get a proper diagnosis done at an expert independent workshop. The guy I trust in Bombay is Sunil Shanbagh. If you want someone closer to you in Thane, search within the Team-BHP Directory.

[SPIKE ARRESTOR]

Originally Posted by icubyx

I took the car to the service center who told me after checking with the laptop that it was temporary error and they reset it. The engine light went away for a few days after that. After a few days, it came back again while driving in a slow moving traffic jam and the car became jerky while accelerating.

May we know what was the temporary error which was cleared?

What you are experiencing is called as an intermittent fault. This could happen when a component is about to fail, say a sensor which is about to go kaput.

Again a trip to the service center and after a diagnostic test, they told me that the ECU and the wiring needs to be replaced as the ECU has been damaged due to some fault in wiring.

They are trying to pull a fast one on you, please consult a FNG and do proper troubleshooting.

Spike

[icubyx]

Originally Posted by SPIKE ARRESTOR

May we know what was the temporary error which was cleared?


What you are experiencing is called as an intermittent fault. This could happen when a component is about to fail, say a sensor which is about to go kaput.



They are trying to pull a fast one on you, please consult a FNG and do proper troubleshooting.


Spike

I don't know the error. The technician just said it was a temporary error and has been cleared, so not to worry - but didn't explain why it happened. However the light came on again after a few days.

Sorry but what is an FNG?

Thank you!

Sounds like a very incompetent workshop to me. They're clearly throwing things at the wall, in the hope that something sticks. The check engine light could be due to a wide number of factors. I suggest you get a proper diagnosis done at an expert independent workshop. The guy I trust in Bombay is Sunil Shanbagh. If you want someone closer to you in Thane, search within the Team-BHP Directory.

Thank you! I will check the directory and if don't find one in Thane, I will definitely check with Sunil Shanbagh

[Jeroen]

Please ask them for the exact error code. Only way to make some sense of it.

There is no such thing as a temporary fault mentioned in the various definitions the OBD protocol uses. There are pending faults caused by intermittent faults.

Pending codes are caused by intermittent faults or faults that the PCM needs to see happen in two consecutive warm-up cycles to set the code. If the fault does not reappear within 40 warm-up cycles, the code will be cleared from memory.

You might be dealing with one of these, impossible to tell without the actual fault code. I find it very difficult to belief the ECU is damaged. Ask them how they reached that conclusion. There is no fault code that says the ECU is broken and it and all the wiring needs replacing.

Troubleshooting and doing a proper diagnosis with an OBD scanner is a very specific skill. Requires a lot of knowledge, experience. Especially when you are faced with intermittent faults.

Best try someone else.

Good luck
Jeroen

[icubyx]

Hi all, thank you for your advice. I got the car scanned from another garage and it indicated the following:
P0340 - Powertrain
Camshaft position sensor A circuit (Bank 1 or single sensor)
The mechanic is looking into it. I will keep you posted on the outcome.

[Jeroen]

Originally Posted by icubyx

Hi all, thank you for your advice. I got the car scanned from another garage and it indicated the following:
P0340 - Powertrain
Camshaft position sensor A circuit (Bank 1 or single sensor)
The mechanic is looking into it. I will keep you posted on the outcome.

Ok, now we are getting somewhere. On most cars this code indicates a problem somewhere in the circuit up to and including the camshaft position sensor. But not only the camshaft position sensor. The sensor can be tested reasonably easy and fairly reliable on its own. Although it could be something else, experience shows that in probably 8 out of 10 cases it is the CPS. Even if they test ok on their own, that is not necessarily enough. Problems with the CPS might only occur when they warm up.

So the mechanic needs to check the whole circuit for faults, poor connections and if all that checks out, I would replace the CPS.
Good luck
Jeroen

[svsantosh]

Intermittent faults are a technicians worst nightmare. Most common reason for larger garages to shoo you away because they cannot wait for it to come up. You may see it till the time you enter the workshop, moment you give the keys to them it will vanish, what are the odds!

Most likely cause can be a badly plugged in sensor connector, less likely is a bad sensor, rare occurrence can be a harness change or a ECM replacement.

[icubyx]

Hi All, Update on the intermittent engine light - I took it to a local garage and he repaired the wiring . Looks like there was an issue with loose wiring. The engine light is gone and no error code showed up on scanning again. Keeping fingers crossed it won't show up again. Thanks for all your advice!

[SuperSlick]

Hi All, sharing my experience & TATA Motors' analysis and fix on the Engine Malfunction Light that came up today in my 1500KM run Tiago XZ+ Petrol MT. The car had just undergone 2nd free service per specified timelines by TATA Motors/Dealership on Feb 11, 2023. Since 2nd service it had only run about 200 KMs in city traffic.

Here's the error code and the specific sensor in the Engine Bay that the technician pointed out and fixed in front of me.





Per him, it was a loose sensor which he fixed and after scanning and Revving the engine on higher RPMs for about 5 seconds per the analysis recommendation, the issue got resolved and engine malfunction light went away. Re-scanning the car did not throw up the error again or show any other issues. There is a similar sensor towards the bottom on the under side of the engine. The scan will point out the exact location.

All of this was diagnosed and fixed within 10 minutes. Need to see if this recurs in future though per technician it should not. Fingers crossed!