TCS Issues continue - Tech look

[jamesmost]

replaced tcs computer from same year . still throwing 3 codes at different times 6,7,13 lr wheel sensor, rr wheel sensor, secondary throttle position sensor..can the 2ndary tps not adjusted properly be causing my woes ?wes suggest because of the 408 maybe the readings of wheel speeds front and rear were freaking out the computer.

once again befor the system shuts down I can:pull away tires spinning w/tcs on, but if i power brake the tcs operates properlywhen the system is down abs is off as well

[elwesso]

heres my theory:

The ABS system (TCS cars basically are just 4 channel ABS) is configured with the 3.54 gears... Since the computer is configured at this rate of spinning, it may throw everything off..... With the stock gears, it is allgood, but with the 4.08 it thinks the rear is spinning faster (which techncially it is, compared to thef front)... Since both rear sensors are spinning at the same rate, it compares it with the front, and then assumes that one or both of the sensors is messed up...

Since you cant replace the pinion gear on the speed sensors in the rear, you may be able to change the sensor ring to one made for a 3.54... From the factory, the Q has a 48 tooth sensor rotor front and rear. The 300ZX has 46 teeth.. if this is the case, its likely to think that the front of James' Q has a 48 tooth rotor up front and a 46 tooth in the rear...

First thing id do is measure the resistnace of the sensors as outlined in the FSM on page BR 86.

I see 2 ways to diagnose this....

1. Count the number of teeth on the front and rear sensors...

2. Compare the voltages of the front and rear sensors.... this would probably be the easiest way to start since you really dont have to take anything apart, you just have to stick needles on the harness and put your VOM up there. Problem is how do you compare all 4 voltages while your moving?? You have kids, right????

According to my theory, the voltages at the TCS control unit should be the same FR/FR; as well as RR/RL, but the average voltage between front and rear should be different....

im inclined to think that the secondary TPS problem is seperate... i dont want to worry about that now...

[Q45tech]

The ABS system (TCS cars basically are just 4 channel ABS) ??

ABS system removes brake presssure [from locked wheel] while TCS system adds additional brake pressure to the rear wheels.

Really the most opposite of things............ABS cannot add brake pressure and TCS cannot remove it.

The sensors are the same [measureing wheel rotational speed] but the software and accumulators act very differently.

[3Q Jay]

good feedback James--I'm debating hto pursue the 4.08, but i really want everything still working right.

one point i'd like to clarify: 3.54 or 4.08 won't matter on TCS cars due to the fact that the output shafts (where the sensors are on TCS cars, and James' diff ) don't care. just the input shaft is making more revs (ABS location on non-TCS cars, or so I'm told....

Wes may be on to somethinbg about the number of teeth in the 'stator'. if that's different, would certainly freak things out. All i know is the TCS is EXTREMELY sensitive on the active to even the slightest wheel spin.

[FarFetched]

ABS/TCS both count wheel spin difference. As long as all 4 (or 2 wheels) rotate at the same speed (included differentiation arond corners) ABS shouldn't act up. TCS is more complicated system because it relies on throttle input as well. I've never seen ABS mulfunction when diff erentialratio had been changed and/or bigger tires installed. It is possible, however, that computer might missinterpret data and kick in ABS sooner or later. There might be something wrong with ABS tone rings on output flanges or front wheel tone rings!Cheers!

[elwesso]

im wondering if the front and rear things for the Y33 and Z32 N/A were the same.... and on the G50 theyre different.

[FarFetched]

im wondering if the front and rear things for the Y33 and Z32 N/A were the same.... and on the G50 theyre different.

After I swapped 4.08, I never encountered ABS/TCS problem. I had more frequent TCS blinking under hard accel though! This leads me to believe that z32 and Y33 tone rings are the same teeth count!Cheers!

[Q45tech]

TCS looks at the rear wheel rotation speed vs speedometer and the range of all four sensors to determine which rear wheel is spinning faster than allowed by vehicle speed.

ABS does the same thing [uses the same sensors] except it looks for the slower than average tire.

http://ej.iop.org/links/rg87xN...8.pdf

Since both systems depend on the tire and the road.............failure to use an oem soft fast wearing tire or using a tire out of it's temperature friction curve results in the software failing to function as designed................it still engages at the same 10-20% slip but the speed is faster or slower.

[Rex]

I still get the TCS/SLIP lights at times, for example, I may get them within 100 feet of leaving my neighborhood, or (like Sat) 45 miles after leaving my house???

[jamesmost]

I still get the TCS/SLIP lights at times, for example, I may get them within 100 feet of leaving my neighborhood, or (like Sat) 45 miles after leaving my house???

did u replace thr rr sensor ?? does the system work properly before it disables itself ??

[jamesmost]

TCS looks at the rear wheel rotation speed vs speedometer and the range of all four sensors to determine which rear wheel is spinning faster than allowed by vehicle speed.

ABS does the same thing [uses the same sensors] except it looks for the slower than average tire.

http://ej.iop.org/links/rg87xN...8.pdf

Since both systems depend on the tire and the road.............failure to use an oem soft fast wearing tire or using a tire out of it's temperature friction curve results in the software failing to function as designed................it still engages at the same 10-20% slip but the speed is faster or slower.

any suggestions on what to try next ??

[Q45tech]

The tone wheel [reluctance wheel/magnet sensor] will create a known frequency based on number of cogs and tire load circumference and speed.

Ao 60 mph a 26 nominal [25 loaded]=~~78.5/1=~~6.55 feet 88/6.5= 13.435 x # of cog teeth [with 35 teeth = 470 Hz].

Driving along you have 4 [3 sensors] singing.

On the same axle a brand new tire 11/32" and a 2/32" worn out tire would have a 2% difference in the tone frequency. Inflation extremes might add another 2%.

On the front when you turn there is a difference between tire rolling distance inner vs outer tire.

Anyway 10% difference or slip % vs speed sensor reference is where things start.

[Rex]

did u replace thr rr sensor ?? does the system work properly before it disables itself ??

Not yet ... still need the special wrench/socket so i dont' have to drop the exhaust or rear axle.

Yes, it works before the lights come on.

[jamesmost]

Not yet ... still need the special wrench/socket so i dont' have to drop the exhaust or rear axle.

Yes, it works before the lights come on.

rob just said that it was a # 13 code which is secondary throttle position sensor -- check ur codes..........