Isuzu Trooper Owners Club UK™

Gribble

Anybody know how to see what causes P1631 - immobilizer wrong signal received at ECU to be put up when the immobilizer says correct transponder key
and signal sent ? Tech II readings.

The wire has continuity between the immobilizer and the ECU.

Think it has to be a new ECU ? Confused

Other symptoms - no check light ,no glowplug light,no supply to Tech II from diag socket. Engine will turn over but injectors disabled ,rail pressure at 0%.

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andrewthomas · ** Joined: 11 Jan 2009 Posts: 99 Location: mid cornwall

As no expert, i would check the power to the ecu such as the fuse. Ive read the brake light fuse is also the ecu feed. A moderator will explain in more depth im sure.

Gribble · Posted: Thu Feb 05, 2009 23:56 Post subject:

ECU plug J 3 reads - Pin 1 11.98v - Pin 2 11.97v - Pin 3 ground 0.0023 ohms - Pin 4 ground 0.012 ohms. Pin 5 - scales in miliamps +/- no fixed reading.

Dont think its a ECU supply problem more of a serial bus /command issue.
Got 5vdc + on J1 3 and 4 in the red plug upper part which is in spec but can pin 7 here have a value ? is it the upline from the immobiliser ? bit stuck now Confused

TimBanham · Posted: Fri Feb 06, 2009 9:48 Post subject:

If it is an ECU job there is a guy that advertises in eebuygum who is based in Derby who will recon yours for <200 supposed to be guaranteed to fix as well
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eithan h · Posted: Fri Feb 06, 2009 20:04 Post subject:

defo check that brake light fuse as it feeds the main relay as well as tech2's diag socket which is normally the problem when tech2 won't power up from the car

Gribble · Posted: Fri Feb 06, 2009 21:03 Post subject:

12v on pin J2 -10 at the ECU so that brake light fuse circuit is ok .

Got 12v on J1 -10 too so all feeds in are ok just the outputs are off.

Going ECU change I think here .

eithan h · Posted: Fri Feb 06, 2009 21:08 Post subject:

have you got it on a battery booster at all and what year is it?

Gribble · Posted: Fri Feb 06, 2009 21:43 Post subject:

1999 3.0 manual Uk car and no booster just the batterys charged up.
The reason I think its an ECU fault is that if the immobilizer (from techII -body- data display )says its active and alls ok no DTC,s and the engine cranks over but wont let any injection oil pressure build its like half a signal is there cos it should not let the engine crank if the wrong signal P1631 is received at the ECU.

Also if Tech II is powered up off the ciggy socket when the ign is on the check light comes on then starts to flash at 2 second intervals which is an immobiliser circuit fault I think but could be the ECU reading it wrong . Confused

eithan h · Posted: Fri Feb 06, 2009 21:46 Post subject:

it should crank over i think it's just the ecu won't enable the injectors if the immobiliser signal is wrong, if you clear the code does it come back?

it does sound like the key needs to be coded does it have 2 keys on the keyring?

they are a bit weird i think it's the 3.0l that if you start it on a good key and switch off then straight away start it on a non coded key it will still run, they have a timeout thing built into them where it has to be off for a certain amount of time like 10 secs before it will read another key for starting.

i've not had to replace any of the immobiliser system yet i don't think on a 3.0l so i'm surprised it's giving you problems whats the story with it did it just not start one day or did it die when running?

Red Robbo · Posted: Fri Feb 06, 2009 22:28 Post subject:

WTF....

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eithan h · Posted: Fri Feb 06, 2009 22:51 Post subject:

it's odd because you have everything where it should be is just the fact it won't start?

Gribble · Posted: Sat Feb 07, 2009 14:15 Post subject:

Was brought as a long standing non runner . would think it just died one day and not been sorted since.

It has the two original transponder keys and a working fob but the ignition barrel has been changed and only a mechanical key works it. One t'key is taped to the aerial ring and tucked under the dash,oddly the t'keys still fit the door locks Confused

The check light only comes on and flashes when tech II is powered from the battery direct ,this also enables #2 ECM feed relay which allows cranking . no power in the DLC socket pin 16 at any time otherwise.

The only DTC that is present is the ECU saying wrong im signal ,if I clear this it comes back sometimes with no signal received but mostly wrong signal received.

I cant see any loom damage nor any attempts to bypass stuff.

Tech II shows correct keys are present and correct transponder signal sent.

From reading the manual it seems that there is an uplink and downlink between the im and ECU and both these wires have continuity.

When cranking tech II shows that the rail oil pressure is at 0% which the manual says is correct if the ecu gets no correct signal from the im but the im from tech II readings says alls well start is enabled !

Thats what leads me to think the ecu is at fault internally . I want to get the 4 digit security code and disable the immobiliser function just to see that it is the ecu.

Thats a handy to know about the im not giving troubles Eithan - thank you.

Wont start and no glowplug light,check light or cranking till powers in the DLC is the main problems.

All thought and comments welcome Smile

eithan h · Posted: Sat Feb 07, 2009 15:04 Post subject:

when you read from the tech2 what does the batt voltage read?

are you using the mechanical key or the other transponder one?

Gribble · Posted: Sat Feb 07, 2009 17:13 Post subject:

Using the mechanical one as its the only one to turn the barrel.

11.9 to 12.01 v .

Will stick all tech's figs up for you today - hoping you see a thing there I have missed Smile

eithan h · Posted: Sat Feb 07, 2009 18:00 Post subject:

excellent can you do it with it cranking though?