4WS Not working. Some debugging already done SOLVED

AeroNotix · Post by **AeroNotix** » Sun Oct 29, 2017 6:13 pm

Hi all,

5th gen 1998 Prelude here. JDM H22A swap (done by previous owner).

Since I bought it the 4WS hasn't worked.

What I've tried:

Reset the 4WS several times.
Retrieved the codes. Always displays code 21 which is:

Code: Select all

 "21      Main Steering Angle Sensor    Rear                   6,13             CU, RSSAS, RMSAS, HC"

EDIT: I've since found the above, while points to the "correct" issue is actually the description from the earlier 4WS systems. The later 5g diagnostics book describes this fault code as "Uneven signals between the main and auxiliary rear angle sensors".

According to the listing I have.

I know it's more of an earlier generation thing, but I opened the ECU to try to find dry solder joints around the relays, there in fact was one dry-ish looking joint. I resoldered all the relay pins but it did not change things.

I've started looking at the wiring, before taking the whole unit off for a refurb. The wiring looks "good". So far I've not found anything especially incriminating.

Some additional questions:

Is it safe to drive with faulty 4WS? I know that Honda added an auto centring/locking mechanism but wonder how safe that actually is?

I assume in certain conditions the 4WS won't actually turn the wheels. I.e. assuming when the handbrake is on, etc. When I try to fix it I am turning the car on, taking the handbrake off and moving the steering wheel. It should turn proper in that situation, yes? After reset the wheels turn ever so slightly, leading me to believe at least mechanically the system works.

Another question, when I sit stationary after a reset and turn the wheel the idle increases, when the idle increases the 4WS light flashes. Additional issue or just a quirk?

89 UKDM BA4 4WS (resto job!) · Post by **wurlycorner** » Sun Oct 29, 2017 7:27 pm

You can drive it with the 4ws not working, but don't do anything at all 'freaking insane' (high speed or serious cornering) because the rear wheels are not mechanically locked, so they will move slightly as the car comes on load over bumps/round corners.

Handbrake has no effect on whether the rear wheels steer or not. if the engine is on, the rear wheels should turn with the front.

Idle speed should increase slightly if you turn the steering wheel while stationary - that's the additional load on the engine due to the power steering pump (for the front wheels)

I assume the 4ws light is flashing because the rear steering isn't behaving correctly?

89 UKDM BA4 4WS (resto job!) · Post by **wurlycorner** » Sun Oct 29, 2017 7:27 pm

I didn't type 'freaking insane' I typed s-p-i-r-i-t-e-d
Gotta love the swear filter on here

AeroNotix · Post by **AeroNotix** » Sun Oct 29, 2017 7:32 pm

Right, that clears up some of my worries driving it. I've only just bought the car so I am not pushing it since I've not learned it properly yet. I have an EP3 Type R for hooning.

So, given my symptoms, is there anything else I can try other than eliminating the wiring, the 4WS ECU and replacing sensors (roughly in that order)?

The sensors are outrageously expensive and one of them doesn't really seem to be available. I can live with the 4ws not working but I do want to have it working.

Post by **Vtecmec** » Sun Oct 29, 2017 8:14 pm

Take a look at the rear rack rod ends, are each about the same length? Could be that they have been adjusted and the rack is not centralised, causing your error code.

AeroNotix · Post by **AeroNotix** » Sun Oct 29, 2017 8:40 pm

Will that cause code 21? They look about right to me. I'll get out the ruler to get a proper measurement.

AeroNotix · Post by **AeroNotix** » Sun Oct 29, 2017 9:08 pm

Both sides are about equal from measuring. Not trying to cast doubt on what you're saying but I can't imagine a small difference in length either side would throw a code. Is that a "thing" with the 4WS? I'm completely new to this and I am just trying to learn.

Post by **Vtecmec** » Sun Oct 29, 2017 9:13 pm

Im pretty sure the rear main angle sensor is in the rear rack, so either faulty or way out of alignment. Given that it works slightly after a reset, my money would be that it's not entirely sure of its electronic position.

I'm not to sure on the 5th gen system, can you do an electronic neutral test?

AeroNotix · Post by **AeroNotix** » Sun Oct 29, 2017 9:14 pm

How do I do that? The term has appeared in my research but I'm not sure I've seen the exact procedure written down.

I'll also get a video of the code being displayed so you can verify I've read it properly as "21".

Post by **Vtecmec** » Sun Oct 29, 2017 9:18 pm

The manual for the 4th gen has loads of electronic testing procedures for the 4ws system. Worth a try?