Check Engine Light On - Codes 16517, 17501, 18669

**willdudeuk** · 08-09-2021,01:47 PM

Car is running really rough idle is bad too.

Any advice how to solve this?

I used ODIS and followed the test plan for the 18669 fault codes.

Went through the test plan and said it was ok.

Not sure what else to look at?

Could it be a mechanical issue?

Or should i be checking the lambda wiring from the Ecu to the fly lead as you have suggested first?

EB26A432-8E9E-4D9A-9E71-F42D2718D7F6.jpg

**Crasher** · 08-09-2021,05:24 PM

Compression and the valve timing checks. Have you cranked it over with the coil packs off but still connected to the harness?

**willdudeuk** · 08-09-2021,06:47 PM

What does cranking it over with the coil packs off do??

**willdudeuk** · 08-09-2021,10:22 PM

Yes I did crank the engine over with the coil packs off and still connected to the wiring harness when we did the compression check? Does this cause damage to the ECU or other components?

Compression check was ok but cylinder 4 was slightly down.

Cylinder 1 150psi 10bar
Cylinder 2 150psi 10bar
Cylinder 3 150psi 10bar
Cylinder 4 137.5/140psi 9.5bar

I’m suspecting maybe the timing is perhaps very slightly out??

I will have to double check and make absolutely sure it’s ok.

**Crasher** · 09-09-2021,01:37 PM

If you crank the engine with the coil packs unable to spark to earth it kills them instantly.

**willdudeuk** · 09-09-2021,04:14 PM

Ah ok well I replaced them anyway with brand new Bosch coils and NGK plugs as well discussed in another post I put up I think.

So when doing compression or check or cranking always make sure the coil packs are disconnected from the wiring harness to avoid damage?

**Crasher** · 10-09-2021,10:29 AM

Yes, very important

**willdudeuk** · 10-09-2021,10:41 AM

No worries I now know and won’t be doing that again.

So think I’m going to check:

1.) Valve Timing

2.) Pre Cat Lambda Sensor (Bank 1 Sensor 1) Wiring (from ECU to fly lead).

3.) Check condition of Lambda sensor (ensure heater circuit operating correctly as well).

Shall report back my findings and hopefully get this rough running issue resolved.

If there is anything else you think I should let me know.

Thanks.

**Crasher** · 10-09-2021,11:50 AM

If the valve timing is OK, you can check the condition of the full system including lambda sensors by generating the readiness code, there is a function for this in ODIS and VCDS.

**willdudeuk** · 10-09-2021,01:51 PM

I did do the readiness check a week ago or so and it passed.

Followed the instructions on VCDS to complete the readiness and it passed.

So perhaps it is a timing issue? Maybe chain has stretched?

Will have to check to confirm.

How easily does the camshaft locking tool have to go into the camshaft alignment holes? (T10171A)

Is there a difference between the T10171 and T10171A?