306 HDi - No throttle response and stuck on 1300 rpm... Have I cooked my ECU? - Peugeot Forums
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Old 13-11-18, 04:46 AM   #1
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Exclamation 306 HDi - No throttle response and stuck on 1300 rpm... Have I cooked my ECU?

Hi all,

I've recently been trouble shooting an issue with my 2000 306 hdi 90. The problem has been a slight but very noticeable hesitation/miss on acceleration through about 1700-2100rpm. It's especially bad at 2000rpm.

I've been looking into a few things - most notably the EGR, the TPS and the MAF.

Today things got a whole lot worse.. I was trying to test the MAF by back probing the plug and reading the voltage output of the sense wire when I accidentally shorted something. The engine was running at the time and it immediately jumped from idle to 1300rpm and stayed there. I turned the ignition off and re started the engine and it went straight back to 1300rpm. I tried to rev it and the throttle did absolutely nothing. It's not reading inputs from the TPS! I plugged the MAF back in and the rpm dropped slightly but only by about 50rpm.

I plugged my OBD reader in and got the following codes:
P0560 - System Voltage
P0190 - Fuel rail pressure sensor circuit bank 1
P0220 - Throttle/Pedal position sensor switch 'B' circuit
P0120 -Throttle/Pedal position sensor switch 'A' circuit

I reset the codes and switched off and on again. Only P0220 and P0120 returned.

I had a look at the live data from the reader and this is what I saw (note the MAF was unplugged at this point)
Attachment 81620 Attachment 81622

Interesting to note the intake air temp was reading 215deg no matter if the MAF was connected or not. Also with the MAF connected the airflow was something crazy like 300gp/s.

I also noticed that the interior clock along with the (after market) stereo had reset themselves like they do if you disconnect the battery.

I checked every fuse on the car (that I know of - are there any other than the engine bay box and the drivers footwell box?) and everything looked fine.

Does anyone have any ideas? Have I cooked my ECU??

Any help is much appreciated.
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Old 13-11-18, 07:17 AM   #2
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Had this on a taxi once the fuel pressure wires shorted on the starter and symptoms were the same faster idle would not rev track was burnt out inside ECU we just repaired the burnt track and all good again.

Open the ecu and have a look and stop probing things
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Old 13-11-18, 07:44 AM   #3
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Quote:
Originally Posted by reliable406 View Post
Had this on a taxi once the fuel pressure wires shorted on the starter and symptoms were the same faster idle would not rev track was burnt out inside ECU we just repaired the burnt track and all good again.

Open the ecu and have a look and stop probing things
Oh wow okay.. didn't realise I could get into the ECU. Is it an easy job to get it out and open it up?
Any tips on fixing a bad track if i find one?
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Old 14-11-18, 05:04 AM   #4
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I ended up opening the ECU and had a realy good look over the board. I couldn't see anything that looked fried.

I've just taken readings from all pins in the TPS and MAF plugs with both the ignition on engine off, and then the engine running. From what I can see there's definitely something odd happening down the line in the TPS wiring. All these reading were direct from the loom side of the plugs whilst they were disconnected.

TPS Engine off - Engine on
Yellow 9.67v - 10.94v
Green 10.63v - 4.95v
Red 5.01v - 5.01v
White 9.67v - 10.93v

MAF Engine off - Engine on
1 Green 5.00v - 5.00v
2 Pink 12.07v - 14.03v
3 Red 4.95v - 4.95v
4 Blank (no terminal in use)
5 Yellow 0.01v - 0.00v
6 White 4.95v - 4.95v

Something I found interesting (maybe because I don't know what i'm really looking at) is that the Red and White wires off the MAF which are meant to be earth wires are reading 4.95v and have no continuity to any earth points I tried. The green wire off the TPS is also reading 4.95v when the engine is running - is this also the earth for the TPS? I understand there's a 5v reference circuit on most sensors but that looks like its the Green off the MAF and the Red off the TPS. Why would the others be reading 4.95v?
Does anyone have a wiring diagram they can share?

I've been doing some further research and discovered (i think) the MAF, TPS and Fuel rail pressure sensor all share a common earth which is prone to high resistance. This could be why i'm getting code p0190. Peugeot apparently approved a mod to cut the earth wires from the MAF plug and re-route them to a new earth. There's some chat about it on the UK 306 forum but I can't share a link cause i'm new.

Unfortunately I live in a place with no pug specialists, and very few euro cars so i'm kinda out on my own. Any more help would be much appreciated!

Cheers
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