94 Volvo 850 T5 Error codes 233 and 433

Post by **Volvofan94** » 01 Mar 2014, 09:24

Hello MVS!

Quick question about two simultaneously occurring error codes my Volvo Turbo 850 is giving me: 233 and 433 taken from the A2 port.

233 Long term idle air trim
433 Rear knock sensor signal

Here are my thoughts on how to correct them:
233: I will check around for breaks in the vacuum lines today. I cleaned my idle air controller and the screen to the EGR Valve last summer; I don't think that would cause a problem...

433: Did some more researching on this one as it's occurred twice this winter. Most threads say it can be a faulty connection in the wiring harness that connects to the rear knock sensor. Where would the rear knock sensor be located on the engine block?

Thanks!!
-volvofan94

Klausc · Post by **Klausc** » 01 Mar 2014, 12:56

There are 2 knock sensors. As you face the engine from the bumper the rear will be on the right. Both are hidden under the intake manifold, just to the left of the starter. "If" you replace the sensor, note the position of the sensor as the new one must be positioned exactly the same. The new sensors come with different wiring.

The 2-3-3 is probably caused by a vacuum leak from a bad elbow. Have you checked the hidden vacuum line coming out from under the #1 runner on the intake manifold?

Post by **Volvofan94** » 01 Mar 2014, 19:09

Thanks Klausc for your suggestions!

If I'm reading your thought on the 2-3-3 code correctly; my car has the system, but it's setup differently from 95 and later 850 turbo models. On my car the vacuum line starts off at the vacuum tree goes through a metal tube on top of the valve cover then eventually connects up with the PTC. If the metal tube were plugged up would it cause a 2-3-3 code?

Below is a link to for more detail on my car's setup.
https://www.matthewsvolvosite.com/forums ... =1&t=59502

-volvofan94

Klausc · Post by **Klausc** » 01 Mar 2014, 19:23

Silly 1994s, and I used to have one! Memories do fade rapidly.

A clogged tube will cause positive pressure in the manifold. Check your boost gauge when warm and at idle, the needle should be very far to the left if the vacuum is good.
If you had the manifold out, check the gasket for leaks as well as the injectors.

Post by **Volvofan94** » 02 Mar 2014, 09:45

Hmm...interesting...never would have thought to check the vacuum gauge reading. Mine is slightly greater than halfway to the left at idle; hot or cold engine (If I drive somewhere today; I'll remember to post up a picture). Usually when the vehicle is coasting the vacuum gauge then goes most of the way to the left.

Hope I'm not getting too off topic, just interested in learning more about my car.

Intake manifold gasket was replaced when I installed a new PCV system last fall.

There are a couple of injectors with broken/missing o-rings (the larger outside o-rings) that go between the manifold and injector. The smaller inner o-rings were replaced when the manifold was reassembled. Wouldn't think those would cause an issue because my NA had a few of those missing and didn't throw the 2-3-3 error code.

-volvofan94

Klausc · Post by **Klausc** » 02 Mar 2014, 09:56

The vacuum leak need not be large to throw the code. Spray some volitile concoction at the base of the injectors and see if the idle changes (leak), or even spray some water at the base of the injectors and see if the water gets drawn in.

Post by **Volvofan94** » 06 Mar 2014, 21:12

Thanks Klausc, I'll give it a try this weekend and will post back my findings.

Have some more news, it appears the tube on top of the valve cover could be fully plugged up. The vacuum readings at idle and coasting have risen (further towards the right of the boost gauge). This week the car has been idling rougher than I remember.

-volvofan94