I have an interesting problem. When I start the car everything works good. After a few miles of driving, suddenly the steering servo starts to work really hard, as it dissapeared, and after that HICAS lights up.

Every time is the same story, no matter how many times I start the car, even the engine is warm.

What can be the problem?

Thanks

Mike who has just come over from Belgium had a similar problem. He said it was around 100km/h which is around when the HICAS starts to actuate and power steering went. I suspected there may be a fault in the HICAS PS system such as a leak which is only affected while HICAS is actuated.

 

I wonder if JeffTT or someone can bless us with some science ;)

Mike who has just come over from Belgium had a similar problem. He said it was around 100km/h which is around when the HICAS starts to actuate and power steering went. I suspected there may be a fault in the HICAS PS system such as a leak which is only affected while HICAS is actuated.

 

I wonder if JeffTT or someone can bless us with some science ;)

 

I have some kind of leaks under the car, since it's in the garage. Nothing big, few drops, but something is leaking. I checked everything, all fluids are OK. Once the clutch fluid was low, and it stopped to work, but after I added the necessary quntity, it's working ok.

I wonder if JeffTT or someone can bless us with some science ;)

 

Ok no real mystery here, the power steering system and Hicas are linked by a common ecu, the euc takes signals from various sensors and it reacts with hicas operations when required to stabilise the car in corners etc. The power steering is speed sensitive and has a fluid solenoid valve which can switch the fluid pressure from a hard setting for high speed to easy setting for low speed maneuvering.

 

So if a failure in a sensor input that effects the HICAS only, all that would happen is the HICAS light comes on which denotes the system has detected a fault and has shut down.

 

If a fault or sensor input fails that effects both the HICAS and power steering then again the HICAS light will come and disable the HICAS but also default the power steering to the hard setting.

 

So given the symptoms it appears to be the later issue, the most likely is a speed sensor signal, what you need to determine is if the speedo is still working when the fault occurs, if it is working it suggests the signal is lost after the speedo unit, this will most likely be the speedo head output. If the speedo is not working, then it could be the speed sensor, the speedo head input or if an import and fitted with a kph to mph converter, a few basic checks should determine what the cause is.

 

Hope that helps

 

 

Jeff

 

 

Here is a link to a thread I did a few years ago about how to repair speedo heads:

 

http://www.300zx.co.uk/forums/showthread.php?175083-Speedo-soldering-tech&highlight=speedo+tech

 

Below is some more pics of the speedo parts:

 

 

 

 

 

Speed sensor, ( auto type shown )

 

 

Manual gearbox speed sensor location

 

 

 

Edited October 20, 20169 yr by JeffTT

It s exactly how you say, my speedo is working randomly only. Most of the time not. So this is the problem...

Now I need tofind the right person who is capable to find the broken part...

 

By the way form where I can order the speed sensor?

It s exactly how you say, my speedo is working randomly only. Most of the time not. So this is the problem...

Now I need tofind the right person who is capable to find the broken part...

 

By the way form where I can order the speed sensor?

 

Not common for the speedo sensor to be the problem, usually further down the circuit, however an intermittent fault with the sensor can happen when the end piece comes adrift in the picture, this can be re fixed in place without any need to remove it from the gearbox.

 

On the rare occasion of needing a new speed sensor be aware there are different ones for auto and manual, and different again for non turbo and twin turbo.

 

 

Jeff

An old thread I know...but after an extended bit of driving across broken tarmac (100 yards or so on an M56 contraflow using the hard shoulder) I suddenly lost my speedo...completely dead...this was followed by the HICAS light illuminating and heavy steering...and of course the CC wouldn't lock on.

 

The following 200 mile journey home was very interesting...with the myriad of variable speed limits.....and no idea how fast I was going!

 

I pulled into services to check and there was no power steering fluid loss.

 

From the thread above (and the others cited)....is my problem most likely to be:

 

A A dry solder joint on the back of the speedo head ..........(I have removed and inspected it but cannot see anything untoward)

 

or

 

B A loose connection on the speed sensor ...jarred by my 'off roading' session

 

or

 

C A failed speed sensor

 

or

 

D Something else?

 

 

BTW after stopping at the services to check for fluid loss...back on the motorway...no speedo...HICAS light remained off for about 2 minutes.

 

Starting the car yesterday on my drive the power steering was back....haven't driven it since and have dismantled the dash to get the speedo head out.

 

Jeff (oh wise one)...please advise :helpsmilie:

Ha ha o wise one indeed, you need to do some tests to determine what you already know, the problem is been caused by a loss of the speed signal.

 

It could be the speedo head input / output or prior to the speedo head, easy way to determine is have the rear wheels jacked up off the floor by a couple of inches, then you can make voltage tests on the back of the speedo whilst effectively driving the car, albeit stationary and see where the issue is.

 

I will do a little diagram later when I am at my other pc, do not worry we will get its sorted between us.

 

Jeff

So with the voltmeter set to 12volt or less and AC not DC you earth down the black lead and use the red lead to probe screw A for speed signal input, with the engine running and the car in first gear raise the engine revs slightly and your looking for a reading of maybe 1 to 3 volts. If you get no reading at position A and assuming there is no delimter ( jap spec ) then the speed sensor in the gearbox is suspect.

 

If you get a speed signal at screw A then try screw B this is the output from the speedo head that feeds all the other modules such as auto box, cruise control etc. if you get no signal here then the speedo is at fault.

 

Going back to a speedo delimiter, if one is fitted it will be cut in to the A line to connector position either on the speedo track or in the loom, you will need to check either side if this to prove that part of the signal route.

 

Hope that helps.

 

Jeff

 

 

 

 

Thanks Jeff

Jeff....A quick question...your instructions above state using the multi meter in AC mode....just to check that isn't a typo...not doubting your knowledge...just seems to be opposite of what one would expect!

 

I have tried the test as above and get no signal at screw A....and also none at screw B...but I guess if there was no signal into A there wouldn't be one out at B!

 

Apologies for being a little dense around this...:biggrin:

 

Gary

Jeff....A quick question...your instructions above state using the multi meter in AC mode....just to check that isn't a typo...not doubting your knowledge...just seems to be opposite of what one would expect!

 

I have tried the test as above and get no signal at screw A....and also none at screw B...but I guess if there was no signal into A there wouldn't be one out at B!

 

Apologies for being a little dense around this...:biggrin:

 

Gary

 

Yes AC is correct, I know it seems odd but there it is, if your getting nothing at A that is the speed signal input, just check you do not have a kph to mph converter connected into the loom before the plug, if not then its a loom issue to the speed sensor or the sensor itself ( less likely ) there are connections under the car by that could be the issue.

 

Jeff

Thanks Jeff...UK car so no converter.

 

Have already had the speed sensor out and the end isn't blown and the teeth all good....I suppose I could spin the sensor with a meter on it to see if it is generating a signal?... otherwise it must be a connection...seeing as the failure happened after a 100 yards or so over broken tarmac at 50mph!

Thanks Jeff...UK car so no converter.

 

Have already had the speed sensor out and the end isn't blown and the teeth all good....I suppose I could spin the sensor with a meter on it to see if it is generating a signal?... otherwise it must be a connection...seeing as the failure happened after a 100 yards or so over broken tarmac at 50mph!

 

Yes you could check the sensor with a meter, however the seldom fail as a simple item, there is a speed signal on the ConZult plug, try there to see if it is present there, if it is, then run a temp cable up to the speedo head from it and would make for a quick fix.

 

Jeff

Have removed the speed sensor and tested the voltage which I understand should be between 1-5vac....showed very high resistance of around 21...and when spinning the sensor it is very 'rough' and notchy which doesn't feel right....so have decided to replace the sensor....I have seen new ones between £45 - £150....the £45 one states it is for a TT 1995-1996....will this fit?....are there any differences between the 1990-91 and 95-96 models?

 

Happy to try a 'used' sensor if anyone has one (as they rarely fail)

 

Thanks

 

Gary

Have removed the speed sensor and tested the voltage which I understand should be between 1-5vac....showed very high resistance of around 21...and when spinning the sensor it is very 'rough' and notchy which doesn't feel right

 

Thanks

 

Gary

 

 

The notchy feel is correct, what your feeling is the stator moving in the field windings, as the magnets are permanent one`s, you will be inducing a magnetic field when turning it and that`s what makes it feel like that, if you connect the tester to it ans spin as best you can and get a reading then it is working ok.

 

Jeff

Not common for the speedo sensor to be the problem, usually further down the circuit, however an intermittent fault with the sensor can happen when the end piece comes adrift in the picture, this can be re fixed in place without any need to remove it from the gearbox.

 

On the rare occasion of needing a new speed sensor be aware there are different ones for auto and manual, and different again for non turbo and twin turbo.

 

 

Jeff

 

SO it turned out that the speed sensor is broken, that is causing the problem.

I will order a new one.

Jeff any ideas I have a erratic moving Rev counter any ideas please

The rev counter takes its signal from the cas unit which also is the trigger point for the coil packs / spark plugs if the engine is running ok without revs rising and falling then it can only be one of two things, an issue with the signal cable / connector on the back of the cluster or the rev counter itself, check all the connections are firmly plugged in on the back.

 

Jeff

Edited February 5, 20196 yr by JeffTT

I have had the same issue with the speedo playing up over the last 10 years, but only very occasionally, now it has completely given up and the HICAS light comes on after a couple of minutes of driving just after the steering becomes heavy.

I checked the sensor and the black cap is fully in as it should be, so I guess the sensor could have finally packed up. Added to this the odometer stopped working yesterday.

I had ordered a new sensor for my UK TT manual car just in case the sensor was the problem, but the faulty odometer now makes me think something else is faulty.

Rev counter is ok as is the boost pressure gauge.

I also have an Apexi boost controller and that shows the revs and boost, but the speedo on this has packed up as well recently.

Can anyone help, and actually I really need to find a mechanic who can work on my car with a good degree of knowledge of 300ZXs, just seems to be impossible these days and I desperately want to keep the car on the road having owned this one for 21 years. Prepared to go anywhere within 100 miles of Suffolk.

 

 

The odometer runs off the same signal path as the speedometer. Check the speed sensor wiring by the gearbox, the harness, connector (inc corrosion) and

wires going into the sensor itself can get damaged and go o/c. Make sure the connectors on the back of the gauge cluster are properly seated and good.

The speedo gauge itself has a signal processing function from the speed sensor (analogue) to the electronics for the ECU/HICAS/Power Steering/Cruise Control

etc and the odometer and they do fail. Repair is difficult and replacement with another s/h working gauge is the only option.

The FSM check for the speed sensor itself:

el-44.pdf

It is a bit of a haul but a trip to Jim@PowerZed near Bristol is the best bet to keep your car in fine fettle - it will be well worth the effort.

Edited July 13, 20214 yr by AndrewG

Thanks for the advice - I have received the new sensor and once installed I guess the next stage is to check the gauges if no luck. Bristol is a fair journey from Ipswich but I may not have another  option. 

 

On 16/03/2017 at 22:05, JeffTT said:

So with the voltmeter set to 12volt or less and AC not DC you earth down the black lead and use the red lead to probe screw A for speed signal input, with the engine running and the car in first gear raise the engine revs slightly and your looking for a reading of maybe 1 to 3 volts. If you get no reading at position A and assuming there is no delimter ( jap spec ) then the speed sensor in the gearbox is suspect.

 

If you get a speed signal at screw A then try screw B this is the output from the speedo head that feeds all the other modules such as auto box, cruise control etc. if you get no signal here then the speedo is at fault.

 

Going back to a speedo delimiter, if one is fitted it will be cut in to the A line to connector position either on the speedo track or in the loom, you will need to check either side if this to prove that part of the signal route.

 

Hope that helps.

 

Jeff

 

 

 

 

@JeffTT Is the signal that enters the speedometer at (A) the same as the one that comes out at (B) and is sent back to the other components? Or is it processed by the speedometer's electronics?

If I connect (A) directly to (B) without going through the electronics, does this allow the other components to function?

I'm asking this because I would like to create a digital speedometer without losing options like HICAS and cruise control.