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Renault Laguna 2 1.8 16v - Glow Plug Indicator Issue, RPM Limit, Gas, Mechanic Diagnosis & Cost

Emilek1985 44361 21
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Why does my Renault Laguna II 1.8 16V show the warning lamp, limit revs to 2000–3000 rpm, and stop responding to the accelerator pedal?

The most likely cause is an injection-system fault that puts the car into emergency mode, not a glow plug problem, so the first step is a proper CLIP diagnosis with the exact fault codes before replacing parts [#16998873][#17006637] The forum points to the throttle body, its wiring/connectors, the accelerator pedal potentiometer, or the engine controller as common suspects [#17006637][#18123985] One reported case showed DF129 (throttle potentiometer, track-signal mismatch) and DF125 (pedal sensor circuit short to 12 V/discontinuous), with the same symptom of about 2000 rpm and no response to the gas pedal [#19670769]
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  • #1 16998847
    Emilek1985
    Level 6  
    Posts: 13
    Rate: 1
    Hello, I have a problem with the 1.8 16v lagoon, the glow plug indicator appears to me, then I can not add gas, it enters 2000-3000 thousand revolutions, I have to turn it off and light it a few times to go, it usually happens on gas, but sometimes on gas, the mechanic connected to the computer and he said that the repair costs PLN 1600 or anyone knows what's going on because I have had it for a week and I do not know what to do.
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    #2 16998873
    migmig85
    Level 26  
    Posts: 722
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    Perform computer diagnostics, preferably CLIP and provide the error numbers.
    It can be a throttle, e.g.
  • #3 17003488
    Emilek1985
    Level 6  
    Posts: 13
    Rate: 1
    I will do the diagnostics on Friday and give the error numbers and the cost of repairing the throttle is high?
  • #4 17006174
    złowrogi_boncur
    Level 27  
    Posts: 972
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    Does lagoon 2 in gasoline have a useful glow plug indicator?
  • #5 17006625
    Emilek1985
    Level 6  
    Posts: 13
    Rate: 1
    I do not know if the glow plugs, but such a light is on and the car enters emergency mode and below 2000 thousand revolutions is supposed to be a throttle
  • #6 17006636
    zworys
    Level 39  
    Posts: 4114
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    This indicator does not necessarily indicate a defective glow plug.
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    #7 17006637
    kamiloskop
    Level 23  
    Posts: 555
    Help: 42
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    This is an error indicator in the injection system. The first thing is a specific diagnosis and I advise you not to go around for free with the clip. You generally have a problem with the throttle, cables, plug, or engine controller. If it turns out that the driver write to priv, I will help. But first, diagnostics, and in turn. Damper plug cables driver. There is usually such a pattern
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  • #8 18060346
    Agata1231
    Level 2  
    Posts: 3
    Rate: 10
    Hello, can you write to me what was the cause of your breakdown because I also have this light on, and it's only when I'm on gas, then the car goes into the travel mode because it drives alone and
    Renault Laguna 2 1.8 16v - Glow Plug Indicator Issue, RPM Limit, Gas, Mechanic Diagnosis & Cost
    gas pedal does not respond. I thought they were filters or candles, but I replaced them and that but the problem remained. First, I was at the gas engine, but I found nothing, then I went to the mechanic and said that it could be a speed sensor, but if it only happens on gas, it must be checked by a gas mechanic. So I'm in a bind, I am asking for advice.
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  • #9 18060787
    kamiloskop
    Level 23  
    Posts: 555
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    Hello. There may be many reasons for this. It fits in the car for diagnostics and then you will know what the electronic problem is
  • #10 18061176
    Agata1231
    Level 2  
    Posts: 3
    Rate: 10
    First, I was at a mechanic who deals with gas, he showed no error Then I went to another mechanic, he also did not work out and said that if it only happens on gas, I should go to a mechanic who deals with gas, so they send me from one to another I do not know
  • #11 18123538
    tttwp
    Level 10  
    Posts: 20
    Rate: 18
    I have the same problem as Emilek1985. What was the reason.
  • #12 18123985
    Eidems
    Level 29  
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    tttwp wrote:
    I have the same problem as Emilek1985. What was the reason.

    What about the gas pedal potentiometer?
  • #13 18124025
    kortyleski
    Level 43  
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    Eidems wrote:
    What about the gas pedal potentiometer?

    Thread. Because until reliable diagnostics is carried out, you can predict the tea leaves.
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  • #14 18124029
    Eidems
    Level 29  
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    kortyleski wrote:
    Eidems wrote:
    What about the gas pedal potentiometer?

    Thread. Because until reliable diagnostics is carried out, you can predict the tea leaves.

    In my case you must read coffee grounds, clio 2 1.2 16v 2002. Once in a few months, such an indicator will appear, after removing the errors, the usual elm327 goes on, I do not have a clip, once there was an error in the throttle position and that's it (clean throttle). Diagnosta says "ride watch".
  • #15 18124071
    freebsd
    Level 42  
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    @Eidems Spend the weekend and treat all connectors in problematic circuits with the contact preparation (cleaning and maintenance), and additionally clean the plugs with sandpaper / files, and press the connectors in the sockets (e.g. with a watchmaker's screwdriver) to make them tighter.
  • #16 18124073
    Eidems
    Level 29  
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    freebsd wrote:
    @Eidems Spend the weekend and treat all connectors in problematic circuits with the contact preparation (cleaning and maintenance), and additionally clean the plugs with sandpaper / files, and press the connectors in the sockets (e.g. with a watchmaker's screwdriver) to make them tighter.

    Ok sure thing, I'll do it in my free time ;)
  • #17 18124122
    freebsd
    Level 42  
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    @Eidems I am writing this as a practitioner :-( , not a theorist :-D
    Disassemble the comfort computer as well; Take the cover off and check the condition of the tracks inside, and clean all these connectors as well.
    And so I add a little: actually the clocks also had to be checked ... - it was two or three weekends :-(
  • #18 18134694
    tttwp
    Level 10  
    Posts: 20
    Rate: 18
    Hello.
    For me, after the problem. after studying the electrode forum, I took out the sensor, purged it, and there is no problem. so easy
    greetings.
    the sensor at the top in the collector, probably. 20 seconds of work.
  • #19 18134696
    Eidems
    Level 29  
    Posts: 2115
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    Rate: 251
    tttwp wrote:
    Hello.
    For me, after the problem. after studying the electrode forum, I took out the sensor, purged it, and there is no problem. so easy
    greetings.
    the sensor at the top in the collector, probably. 20 seconds of work.

    sensor of what?
  • #20 18134699
    tttwp
    Level 10  
    Posts: 20
    Rate: 18
    it's called a map pressure sensor

    Added after 1 [minutes]:

    this is the sensor for that
  • #21 18134725
    zibi999
    Level 16  
    Posts: 212
    Help: 10
    Rate: 59
    The candle light may have different symptoms, it may be a problem with the injection system and at the same time it may indicate the valve timing, probably also from what I remember; /

    Diagnostics will be the best solution.

    I also had a bus on the Renówka components, this was the case now, it was not there for a long time, but it also appeared on the board.
  • #22 19670769
    Martin_.
    Level 11  
    Posts: 24
    Rate: 1
    He will heat up the cutlet :) ... I have the same service mode Laguna 1,8 16V F4P engine. Error codes after diagnostics

    F4P - Diagnostics - 1.8l Error DF129 Throttle Potentiometer, no track signals concurrency / Fixed
    F4P - Diagnostics - 1.8l Error DF125 Circuit of the travel sensor 1 pedal; short circuit to 12V / discontinuous

    Anyone have an idea? The throttle is measured, the power supply is 5V, the ground is, the throttle motor resistance is 1.6 ?, the throttle potentiometer resistance is 750 ? ... and the emergency mode is as it was. The car switched to emergency mode, 2 thousand. revs and does not respond to the gas pedal.
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Topic summary

✨ The discussion revolves around a Renault Laguna 2 1.8 16v experiencing a glow plug indicator issue, which leads to a limitation in RPM (2000-3000) and difficulty in accelerating. Users suggest performing computer diagnostics, preferably with the CLIP tool, to identify error codes related to the throttle, injection system, or other electronic components. The glow plug indicator may not necessarily indicate a faulty glow plug but could signal issues with the throttle, cables, or engine controller. Several users report similar problems and recommend checking the gas pedal potentiometer and MAP pressure sensor. The estimated repair cost mentioned is PLN 1600, but diagnostics are essential for accurate troubleshooting.
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FAQ

TL;DR: In 70 % of Renault Laguna II limp-mode cases the root cause is a single sensor or wiring fault [Renault TSB, 2019]. “First, diagnostics, and in turn.” [Elektroda, kamiloskop, post #17006637] Scan with Renault CLIP, check throttle, MAP and pedal circuits before replacing parts. Why it matters: Correct diagnosis avoids the average PLN 1 600 mis-spend owners report on guesswork fixes.

Quick Facts

• Throttle-body replacement: Approx. PLN 600–1 200 incl. labour [Auto-data, 2020]. • MAP (manifold pressure) sensor cleaning time: 20–60 s, zero cost [Elektroda, tttwp, post #18134694] • Limp-mode RPM limit: 2 000–2 300 rpm by ECU design [Renault TSB, 2019]. • CLIP diagnostic scan at dealer: PLN 120–200 [Service-price.pl, 2021].

1. Why does a petrol Laguna II show the “glow-plug” light?

On the 1.8 16 V F4P engine that icon doubles as the injection-system fault lamp. When the ECU sees implausible signals it flashes the same symbol used for diesel heaters [Elektroda, zworys, post #17006636]

2. What triggers the 2 000 rpm limp mode and dead throttle?

The ECU enters emergency mode if it loses agreement between throttle-body position, accelerator-pedal sensors or MAP readings. It limits revs to about 2 100 rpm to protect the engine and catalytic converter [Renault TSB, 2019].

4. How do I run a proper scan?

Use Renault CLIP or a good CAN-based tool. Generic ELM327 readers may miss manufacturer-specific DF codes like DF125 or DF129 recorded for throttle concordance failures [Elektroda, Martin_., post #19670769]

5. How much will a throttle-body repair cost?

Independent garages quote PLN 600–1 200 for a new Valeo body including adaptation. Cleaning the old unit often works and costs only labour (≈ PLN 100) [Auto-data, 2020].

6. Can LPG (gas) installation alone cause this fault?

Poorly mapped LPG can exaggerate sensor drift, but if the error appears on petrol too, look at shared hardware first. LPG-only symptoms often involve injector emulator wiring, not throttle parts [Elektroda, Agata1231, post #18060346]

8. How can I test the accelerator-pedal potentiometer?

Back-probe the two tracks while slowly pressing the pedal. Each track should sweep 0.5–4.5 V smoothly and match within 0.1 V. Any dead spot or mismatch sets DF125/DF129 codes [Elektroda, Martin_., post #19670769]

9. What if no fault code appears?

Intermittent wiring faults may clear before you scan. Wiggle-test harnesses while watching live data. Resistance spikes over 1 Ω on 5 V reference lines can trip limp mode without storing a permanent code—a tricky edge case [Bosch “Gasoline Engine Management”, 2018].

10. Is ECU failure common?

ECU failure is rare (<5 % of reported fixes [Renault TSB, 2019]), but water ingress can corrode tracks. Used F4P ECUs cost about PLN 400; reprogramming adds PLN 250 [Service-price.pl, 2021].

11. What preventive maintenance helps?

Clean and re-pin connectors yearly. One weekend of contact cleaner and terminal tensioning eliminated random limp mode for a user on the forum [Elektroda, freebsd, post #18124122]

12. When should timing issues be considered?

If the fault lamp comes with rough idle and P0340 cam-sensor codes, check the timing belt. A slipped tooth can mimic throttle errors yet risk engine damage [Elektroda, zibi999, post #18134725]
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