speed sensor not the answer to PS loss

[mortimer9]

Decided 3wks. ago that the speed sensor was cause of intermittent loss of PS with speedo.Had Infinity tech relace it in my 96Q45(96000mi).Driving home it happened again.I fiquired I'd give more time and it worked without any trouble for the past 3 weeks but now is doing the same thing with the instrument panel reading "transmission failure".What should I do next? kevin

[maxnix]

Not sure about the 1996, but aren't there two speed sensors?

Did he replace the one on the transmission or on the pump?

[Q45tech]

The only speed sensor is in the transmission. This signal goes to rear of speedomter where an IC converts frequency to 0-5 volts to feed all other systems.

[mortimer9]

Right,the speed sensor attaches to the rear side(passenger) of the transmission.What would you do at this point to fix it? kevin

[Q45tech]

Always best and easiest to follow INSTRUCTIONS in FSM for diagnosis. Assuming speedo still works correctly then either the PS presure control computer or solenoid or intermitent pressure valve on PS pump.

Monitor voltage on Consult port driving PS solenoid vs speed to rule out PS computer, monitor PS pressure vs speed to determine other 2 components.

Most common is defective PS computer module that uses 0-5 volts from speedo to pulse solenoid........................all fully and in detail explained in FSM.

Always start by flushing out PS system with brand new ATF as appropriate to local temperature conditions............Dex111g or Mobil 1 Syn ATF.

I forgot about transmission malfuction, if that shows no speed signal then the problem is in the speedo assembly failing to generate the 0-5 on ALL ISOLATED PORTS* or wiring to TCU or in TCU itself.

* The speedo assembly contains an IC which translates pulse from speed sensor an audio tone to 0>5 volts this 0>5 volts is distributed to half a dozen points and isolation transistor protect FROM a short in one system from bringing down all system which rely on 0>5 volt speed signal.

[mortimer9]

Since the speedo fails to work at the same time i experience hard steering problems it sounds like you believe the problem to be contained in the speedo, or wiring to TCU or in TCU itself. I've removed all the trim surrounding the dash and the instrument cluster. What would you recomend doing to trouble shoot and narrow down the source of the problem? It doesnt look like an easy job to replace the wiring harness. I've contacted Scottsdale Infiniti in AZ and they say they no longer sell a replacement speedo. What would be the correct way to test the TCU? I've accessed the FSM but it is still unclear to me.

[maxnix]

Replace the instrument cluster with a similar model (Fed or CA, TCS or not, Active or not) from the same year.

[mortimer9]

Brian,appreciate that.Spoke to Scotsdale.Is it the circute board i need? What is Fed,CA,active or not mean? Where can I pick up a instrument cluster and how much can I expect to pay for it. kevin

[96Qowner]

Easiest (cheapest) to replace the entire instrument cluster with a used one. Check out http://www.car-part.com under "Instrument Cluster or "Speedometer". You should probably stick with a 96 because of the OBDII, but I'm not sure it matters whether it's Federal or California model. Yours is NOT an ACTSUS (active suspension) model. And I don't think you have TCS (traction control) either (yours is NOT a Q45t, right?).

So you need one for/from a non-TCS, non-ACTSUS model.

[mortimer9]

According to my Vin# the production date of my q45 is 9/95 but the title reads as a 96. Do you think I should stick with the 96 speedo? Would I be able to use a 97 speedo. The reason I ask is that I've located a used 95, 97 and 96 instrument cluster. My vehicle does not have active suspension, it has IRS suspension. It is not a q45t.

[maxnix]

Get the 1996 board/cluster. Main concern is whether or not it has TCS.

1997 will not work as it is from a FGY33.

No active suspensionin 1996. All G50 have IRS.
Modified by maxnix at 1:01 PM 1/3/2008

[mortimer9]

B rian&96OWNER,got a used complete assembly for 100 dollars and installed it and is working good.Now will see if the power steering is fixed.Will report if its not.Thanks!Is there asimple way yo change the speedometer reading to accurately reflec actual mi.?

[maxnix]

Not that I know. Check with your dealer, but he may be prevented by law since he didn't install it.

Please report back also if it did repair your problem so a future search will find your solution.

[mortimer9]

Brian,wil do,that is give full follow up. kevin

[mortimer9]

Brian and 96owner to follow up on installation of Speedo(full instrument panel) to correct intermittent loss of power steering.No recurrence in past one month-its a fix.Thanks for the help, kevin

[maxnix]

Thanks for the confirmation. It will be useful for other owners with the same problem.