Lyaison

Hi,
I am new to the forum.
I just purchased new winter tires in a smaller size (was 31" with aluminum rims) with studs and steel rims yesterday. Today while driving it the speedometer gauge jumps from 0 to 100 and back again in park. While driving the rage jumps from 0 to 20. Would my new tires be affecting my speedometer or is a computer issue? ( since I think the speedometer cable was replaced by a sensor after '96 ) Could it be a speed sensor issue?
I am taking it to Autozone after work to have them run the code, if there is one..

Anony

The problem is only with the speedometer, with no other inst. gauges fluctuating? Do you have cruise control?

The problem started immediatly after installing new tires?

Your MIL light is ON?

The instrument cluster has it's own self diagnostics built into it's circuit board. To activate, turn ign. key to On then hold down the odomenter trip button for several seconds. The self diagnostics cycles through testing various ind. lights and gauges, tests only if they're functioning and not for any external operations.

Could be a plug or wire was jared loose, related to the VSS and speedo. The VSS (vehicle speed sensor) is monitored by the PCM that controls the inst. cluster gauges via the CCD bus. When at idle the PCM receives a closed throttle signal from the TPS and no signal from the VSS.

Possible but Less likely your speedo gear is loose or malfunctioning. I'd first inspect the plugs and wires to the VSS and make certain everthing is secured ok.

Lyaison

The Oil pressure sensor went out last week, but it is a five min fix. I ran the diagnoses test on the instrument panel, all gauges responded with the 1/4, 1/2, 3/4, 100%, 3/4, 1/2, 1/4 and 0. Also while driving home, the gauge started responding normally. When I have time, I will check the connections, because the engine sounds normal.

The link to the video shows what was going on.

https://drive.google.com/folderview?...XM&usp=sharing

Lyaison

Thank you!

Anony

Try disconnecting the VSS to see what happens. The PCM shouldn't be reading a signal from the VSS when the engine is at idle.

The VSS is a hall's effect sensor and requires 5 volts to operate similar to the CPS.

The speedo/pinion gear shouldn't be read by the PCM during idle. Possibly something is causing high voltages being sent to the PCM's VSS input, causing an erratic speedometer gauge.

* e.g. short, damaged wire, vss plug-in, faulty VSS, etc.

At idle the PCM receives a closed throttle signal from the TPS. (note: without your foot on the accelerator, the speedometer will become active while the vehicle is moving)

Any problems with the CCD bus, would likely effect all the instrument panel gauges.

_____________

* ___ Visually inspect the related wiring harness. Look for any chafed, pierced, pinched, or partially broken wires.
* ___ Visually inspect the related wiring harness connectors. Look for broken, bent, pushed out, or corroded terminals.
* ___ Perform a wiggle test of the wiring harnesses and connectors while the engine is running.

______________

There is a plastic pinion gear of different colors that match your tire size for correct speedo readings. Stock tires are 215 and 225. Larger tire sizes require different pinion gears for more accurate speedometer and odometer readings.

Tire size, axle ratio, a faulty or incorrect speedometer pinion gear or a faulty VSS can result in inaccurate speedometer readings

__________________ additional diagnostics information ____________

The VSS is used for speedometer/odometer and cruise control functions.
On some vehicles it's also used by the anti-lock brake system.

P0500-NO VEHICLE SPEED SENSOR SIGNAL

When Monitored: Engine Temperature greater than 104 deg F. , MAP vacuum approximately 159 to 169 inches of mercury and Engine RPM between 1400 and 3000 rpm.

Set Condition: No Vehicle Speed Signal for more than 15 seconds on two consecutive trips.

POSSIBLE CAUSES

INTERMITTENT VEHICLE SPEED SIGNAL
5 VOLT SUPPLY CIRCUIT OPEN
SENSOR GROUND CIRCUIT OPEN
VEHICLE SPEED SIGNAL CIRCUIT OPEN
VEHICLE SPEED SIGNAL CIRCUIT SHORTED TO GROUND
VEHICLE SPEED SIGNAL CIRCUIT SHORTED TO VOLTAGE
POWERTRAIN CONTROL MODULE (VEHICLE SPEED SENSOR)
_______

'98+ added an input (AW4) speed sensor. '98+ XJ's have one VSS (vehicle speed sensor) and two transmission speed sensors, an input and output.