fault code 21 .test for primary signal to ECU

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October 5, 200520 yr

my engine dos not start and the fault reader and the ECU are giving fault cod 21 primary ignition signal

and remedy

test for primary signal to ECU

this is chinese to me can sambody please telme wer to start

PS do not lock at rigting mestaqes :headvswal

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October 5, 200520 yr

Code 21 - Wiring Harness or Connector to the Power Transistor Unit (PTU) has failed.

Not sure, but it could also mean that the PTU has failed?

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October 5, 200520 yr

where is it located and haw dos it look i do have a lot of electrical stuf

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October 5, 200520 yr

where is it located and haw dos it look i do have a lot of electrical stuf

A Black box about the size of a Cigarette Packet bolted to the front of the LEft hand Cam cover.

Location is Circled in red :

attachment.php?attachmentid=14901&stc=1

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October 5, 200520 yr

Seem to remember you swapped PTUs when i

was there the other day Rob.Must be harness.

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October 5, 200520 yr

ok nead to look at the whiring again

tanks

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Reverse switch problem

Have you got the right one? The neutral switch and reverse switch are close together and look similar.

By Stephen · 4 hours ago4 hr
UK TT Manual Project

Well I thought things were going too well. The underside has come up well and is looking a whole load better now.
Turns out pre 2009 cars don’t need reverse lights to work to pass an MOT, so I can solve that problem another day. (Switch is working fine, but no signal getting to the rear)
New tyres delivered yesterday and I can just run them down the local fitting shop and have them fitted.
So I thought to myself, I’ll throw on the new pads and discs tonight, and she will be ready to go!
Then the brake pipe broke from the calliper and I had a sense of humour failure.

By RobHowl · Thursday at 22:201 day
Simply Japanese at Beaulieu 19th July 2026

I was just completing my booking but realised that it’s one of my daughter’s 16th birthday! I’ll check what she’s up to and see if I can get a pass! She may come with me, but doubtful. Will update as soon as I know.
Steve 😁

By cybernet · Thursday at 00:002 days
Check engine light comes on and off sporadic.

Those codes are all pointing at a related issue. A/F ratio falling out of range, heater elements within the O2's out of temp range, EGR sensor or exhaust gas temp falling out of range, etc. There is a few areas to consider...
Was any work recently done to the car that may have triggered this? When was the last time you replaced the O2 sensors? Check the O2 connectors and wiring to make sure one of them hasn't contacted the exhaust or melted. Any exhaust leaks especially before the cats? When was the last time you performed an induction service and cleaned the intake, TBs, IAC, etc? The EGR and IACV love to get carbon buildup over the years and can affect flow, similarly can happen to the vac lines to the factory wastegate control solenoid. You mentioned the car felt like it was still running well, so no idle RPM fumbling, hanging, stumbling, etc? Are you running an aftermarket boost control solenoid or OEM? Sorry for the load of questions, but need a bit more to go off of to help point you in the right direction.
Even though the vehicle has considerable low mileage, it's still 30 years old. If it's kept in a garage it tends to handle the elements better than sitting out in the external environmental conditions and will need more routine maintenance and care regardless if it's being driven or not. (i.e. 60K / 120k maint w/ timing belt)

By protoj · Tuesday at 18:483 days
JaiKai - MK2 - Ziggy Build

Time to clean the AC parts as i found a birds nest in it.

By JaiKai · Tuesday at 12:044 days

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fault code 21 .test for primary signal to ECU

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