P1621 p 1621 fault code mgzs td

Engine Management Fault Code P1621 P 1621 MIL Warning Light Error Code

Hi - no help needed (But May Help Others)

On way home a couple of days ago ... engine management warning light came on - car still drove fine
Read code withe Sykes Pickavant ACR4 - revealed P1621
Most OBDII lists - seem to quote....
"Control Module Long Term Memory Performance/ Immobilizer Code Words Do Not Match"

ACR4 quoted....
"Control Module Long Term Memory Performance/ Immobilizer - NO CODE"

Couldn't find anything here .... re what/how fix - origin of cause/failure etc

Lots of other manufacturer forums - had people with "Same Code" fault too (Same/Similar Fault Description)

Lots had the problem , & lots more "Same Here" added comments etc, but...
Several hours later !!
No real definitive definition - as to description of the fault
- or - pinning down - factors that could cause it
- or - how to test - for what/which factor - was causing it
And obviously - with none of the above.... no... how to "Fix It" as a result.

Best I could come up with....(Composite)
1)"The ECU monitors... components/sensor inputs - that are required - for the correct running of the engine"
2) If the ECU - isn't getting what it... wants/expects
You get a P1621 code

Most threads on various makes/models - just either died, petered out, or ended with ... taken to dealers... charged for New ECU or some other obscure "something or other" (Usually Expensive).
.................................................. .........................

Well that all seemed very vague and unhelpful - so whilst I'm quite proficient on mechanical and wires
- when it gets to printed circuits/ECU/SKU's/BCU's etc and any other boxes of tricks, that's a complete - nuther story... as they say.

So when I have problems with - "Other" boxes of tricks - computers, routers, set top boxes.... or anything else, with chips, memory etc
- I usually try the "High Tech Solution"
- switch it off - unplug it from the mains for a good while - pray - then switch it back on again:o)
- nine times out of ten - "Sorted"

And so !
- cleared the code
- disconnected the battery negative/earth lead
- left it that way >>> overnight
(To make sure any..... residual charge "Anywhere" - dissipated)

Next morning
- checked the battery - tickety boo at... 12.6V
(NB some car gizzmos - need a minimum voltage to work - but below that voltage - the car may sill turn over and/or start - so if the battery is weak - might be worth considering changing, >>> before.... looking for more "Exotic Causes")
- also checked cleaned battery terminals, connectors and body earth point
(Always worth doing re many electrical problem - before going any further - as is... checking connectors nice and secure).

Tried starting the car - it did - always a relief :o)
- let it tick over a little while - then gave it a few blips on the revs, followed by 30 secs at a couple thousand revs.
- No warning light - relief Mk II
- switched off and....
- Plugged code reader in - checked for codes.... "All Clear" Relief III.

Returned later in the day - after a decent mixed driving 30 mile round trip
- ran code reader - all clear - relief IV
- after 2 more decent mixed driving/distance trips today.
- ran code reader - still all clear - relief V

Some problems - store fault codes - and if repeated X Times, or after X number of "Drive Cycles" - only then - throws up a fault code warning light (But beforehand - in the interim - will show up on a code reader ... as a pending/stored code).

So .... at the end of today - NO Engine Management Light - No Codes/Pending/Stored
- and all I can say (Tentatively) at this stage.... is

"Problem ... SORTED".
.................................................. .................................................. ...

The three questions - you may have
1 - What triggered the warning light
2 - What was the technical reason - for the fault
3 - Why did the above action... resolve it

To ME personally, and many others - the ANSWER is - "Who cares - it's sorted"
.................................................. .................................................. ....

My "GUESS" on No3 - is .... disconnecting the battery overnight (Or a good few hours anytime)
- in essence causes - a "Forced" reboot,... or in effect a reset -of the "Gizzmos".... back to something equivalent to ...factory settings
- so - any gizzmos and ECU - that may have got .... "Out Of Synch" somehow
- ie - reboot up.... and start off as - "Back In Synch"
and everything's back to.... "Happy Bunnies" again.
.................................................. .................................................. .........

I have no idea if ... YOU GET - a P1621 ... whether the above..... will ... sort your problem out.
BUT - as seen above.... "IT VERY WELL MIGHT" :o)
so probably might be worth a try.
.................................................. .................................................. .........

PLEASE - If you
- do get a P1621 problem & READ THIS
- then... if the ABOVE "Sorts IT" - please add a post below
- if it doesn't work - please add a post below

AS - Subsequent readers with the problem (If like me) see a trend..... of at least - a "Few Positive" outcomes
- then they are more likely - to give it a go too
(Providing they are of course - a fully competent person re dealing with... car batteries).
.................................................. .................................................. .........

Good Luck - Hope somebody finds this.... and it helps them, sometime along the way.
.................................................. .................................................. .........

NB - Whilst disconnecting/reconnecting a car battery - will probably be the simplest job ever.... to anyone on this site or reading this - re car problems/repairs
- if you really do - have no idea what you are doing - get someone who does know - to do it for you
(And by way of emphasis - never touch both battery terminals - always disconnect the negative terminal - as trying to disconnect the positive terminal and any part of your body or tools touches earth/metal part of the car - you may.... live... to regret it).

And finally - doing any of the above is entirely at your own risk and choice
- no advice given, implied or intended - the above is just an account - of my own personal experience,
So - NO RESPONSIBILITY ACCEPTED - for any personal injury or damage to the vehicle, 3rd parties or similar.
Your choice - Your Risk !!

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P1621 p 1621 fault code mgzs td