Renault Megane: Electronic Problems & Solutions

Hi everyone!

I'm having an electrical problem with my Renault Megane 1.9 dTi. It's a 1998 model with the 72 kW engine.

Basically, I'm happy with the car, but the electronic problem is really bothering me (it's been there since I bought the car). The warranty is no longer valid (it's a used car), so I want to tackle it myself, which isn't a problem for me in general.

Ich bin schon mehrere Male damit in der Werkstatt gewesen, aber der Meister is ne absolute Knalltüte und kriegts nicht hin. Er schließt immer nur seinen dümmlichen Prüfkoffer an, und liest den Fehlerspeicher aus. Basta.

The problem can be described as follows:

During the ride, sometimes immediately upon starting or while stationary with the engine running, the vehicle suddenly increases its RPM without any contact with the accelerator pedal. The problem occurs sporadically! Sometimes not for weeks, sometimes several times a day. Occasionally, it becomes so severe that the RPM, for example, remains at 2,500 RPM, and the accelerator is no longer responsive. Pressing the accelerator pedal does nothing; it's as if it's completely disconnected. In this case, the warning light for the electronics also illuminates, which doesn't happen otherwise. The only solution is to pull over to the right, turn off the engine, restart it, and continue. However, this extreme situation is rare.

Since it's an electronic throttle pedal, it was already temporarily replaced as the diagnostic tool indicated it as a potential source of the problem. However, the same error reappeared, and the tool still showed the same error with the new pedal. So, the old throttle pedal was put back in. Then, instead of trusting the diagnostic tool, I decided to investigate the issue myself.

Und jetzt kommt das beste: Ich habe folgendes herausgefunden; Fehler trat auf, also ich stehe mit dem Wagen an der Ampel, plötzlich geht die Drehzahl wieder hoch (immer so auf 1.500 U/min.), ich kann dann zwar normal fahren, aber die Schubabschaltung beim Gaswegnehmen ist komplett weg, und das ist ziemlich nervig. Es war Sommer, also ließ ich mal die Scheibe runter...und siehe da: genau in dem Moment, wo die Endabschaltung des Fensterhebers ins Spiel kommt (man hörts als leises Knacken im Radio) geht der Drehzahlmesser wieder auf Standgas runter, Schubabschaltung wieder da, alles O.K.! Das gleiche Funtioniert auch, wenn ich fahre, das Problem auftritt, und ich einfach bei geschlossener Scheibe den Fensterheberschalter auf 'schließen' drücke, dann knackts sofort im Radio weil die Scheibe ja schon zu ist, und das Problem ist weg. Ist also kein Zufall, ich mach das nun seit über nem Jahr, und fahre damit, aber es nervt langsam. Nur der Fall wenn die Elektronikleuchte angeht und nichts mehr geht (wie oben beschrieben) funktioniert es nicht damit. But it's probably that the Windows operating system completely crashed in the control unit .

The window lifter had to be replaced before due to a broken cable, so that wasn't the problem, because the issue is still present.

Okay, I suspect it might be a grounding issue, but how can I figure that out? Is there a way to measure it, or does Renault have a diagram showing the grounding points?

For a while, I thought the problem might be related to heat, since it only occurred in the summer, but now it's happening even when it's cold.

I just hope it's not the engine control unit, because that would be an expensive repair. But I can't imagine it's that, because the car otherwise runs great, has plenty of power, and still has a very low fuel consumption. So, there's nothing particularly unusual to note. Except that it sometimes smokes heavily when I accelerate, but only for a short time. I was told that it has a kind of particulate filter that 'burns off' in that way. The heavy smoking also goes away quickly.

Also, wenn Ihr mir sagen könnt, was das Problem sein kann, helft mir bitte!!! Ich will den Wagen auch irgendwann mal mit ruhigem Gewissen verkaufen können, ich will keine offensichtlichen Mängel verschweigen. DaThere's only trouble.

I would be very grateful for any tips or solutions you can offer.

Greetings.

Maik.

Hello,

I hope that when the throttle position sensor was replaced, the connectors and cables to the control unit were carefully inspected.
Could water be getting in somewhere? Are the cables frayed, is a pin in the connector pushed in or loose?

Best regards, Rainer.

I'll check it out and get back to you once I've had a look.

Sure, no problem.

Greetings.

Maik.

Just my opinion:

Window lifters and accelerator pedals... Even though the French sometimes develop strange potential when it comes to introducing completely immature, yet incredibly impressive, electronics, this is something really amazing. We once had a Kangoo where the left window would always open when locking the car, which was quite counterproductive and unfortunately couldn't be fixed by the workshop. When we went to Renault for the umpteenth time, they were just receiving a delivery of Lagunas, which was a very strange experience. The entire staff had to roll the cars off the truck because the keyless go system didn't work in any of them. We then took the Kangoo and immediately sold it (with a faulty window lifter).
I thought things were tough here, but respect. It could be worse, as I've heard from you.
Have you ever thought about contacting Auto Bild? They're always looking for stories like this, and there's probably something about special leniency involved if this comes out. It's potentially life-threatening; maybe he'll accidentally floor the accelerator when opening the sunroof at some point...

Delivery of the Lagunas, which was a very strange process. The entire staff had to roll the cars off the van because the keyless go system didn't work on any of them.

hehehehehe....

You need to go to the transporter with ONE card and move the correct car.
If you insert all the cards, all the transponders will malfunction. There will be too many cars and cards in too small a space.

'But the accelerator pedal and window lifter... that's really something. Today, I was also chasing a combined hardware and software error. Because the developers are becoming increasingly stubborn and nobody even talks to each other anymore, it's up to us troubleshooters to give them a hard time... grumble...'

@wassibaby

I'm leaning more towards a hardware defect, as the window lifter is drawing a significant amount of current when it's in the end position. This causes a brief voltage drop, which can damage an A/D converter... or bring it back down to earth.
Try to find another Renault owner to exchange engine control units (ECUs). Alternatively, talk to a reputable dealer. They might be able to help you, or they might already be aware of the issue and any potential warranty coverage.

CU Gremlin.

Hello,

Okay, let's try swapping the battery with one from another car and cleaning the battery ground strap on both sides. Then, check the ground connections of the engine control unit (ECU). It sounds like there's a voltage drop or a grounding issue.

Best regards,
Christian.

Thank you in advance for all the tips!

Okay, I'll check everything out. I've also been thinking about measuring the voltage at the alternator regulator, as there might be something wrong there. It definitely won't work with a new battery, because I already had one replaced before, and the problem was still there. But now, the question: Assuming it's the engine control unit (ECU), how much does that part cost? Is it even worth it? After all, this car has already clocked 165,000 km... and according to the ADAC (German Automobile Club) calculation, its trade-in value is only 4,800 €. Also, the timing belt needs to be replaced, and my brother has already looked up the prices for the parts (the timing belt kit with tensioner, and the crankshaft position sensor with its element, together cost almost 300 €!!!). Of course, we'll do the installation ourselves. The front shock absorbers also need to be replaced, and the air conditioning system needs servicing... I'm wondering if I should even do all of this. Although, I have to say, it's never really let me down.

Okay, so I'll start by cleaning all the ground connections, checking the connectors, and measuring the voltage. I'll try to find someone who has the same control unit and then try to convince them that I need it, but I don't think that will work. Especially since the error is intermittent, it could take weeks for the error to occur.

Let's see. How can we find out which other models might have the same control unit? That would make it easier to find a suitable replacement at a junkyard. Or should we visit a Bosch service center if it's a Bosch unit?

Hopefully, I'll figure it out...

Greetings.

Maik.