Forum:
While driving my car a few days ago the speedo jumped around and then stopped working, as this happened my car made a loud bang and went into limp mode. The following day it worked fine and has done until today when the speedo died and the car went straight into limp mode. I disconnected the battery for 30 mins and on reconnection got about 1 kilometer down the road before it happened again. When it happens. the ODO OFF light flashes on and off. I can still reverse no problem.
The car is a Terios DX, year 2000 with 105900 on the clock. Its an automatic 4X4 4 speed. It recently had a service and the oil and fluid were changed.
I have looked into this online and see that there may be many reasons for the problem. Just wondered if someone can give me advice. I'm not very mechanical 
Most likely the speed sensor
Most likely the speed sensor as this provides both the ECU and the speedo with a signal, being an auto means it relies on the speed sensor to work in conjunction with other sensors for the engine management system to work correctly, and to provide the gearbox ECU with the correct information so it works effectively, and onviously the ABS and traction control if its fitted.
Theres only one way to identify the problem, have the ECU read for fault codes and this should confirm things.
It could be the sensor itself, the wiring damaged, the connections at the plugs corroded, or even damp in the plugs or wiring.
Buy a cheap-ish OBD code
Buy a cheap-ish OBD code reader (iso 14230 kwp2000) and see what it may say. Well worth the £35-£80 spent on one, that's what Garages would charge just to tell you anyway, plus you still have it for future reads or sell on to cut your losses
Report back what the code or codes are?
Oh and when you say it made a loud Bang, can you elaborate more? Was it like something electrical blowing or metal failing??
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Current- 04 Silver YRV TURBO
Past- 91 Charade GTti, 89 Charade GTti, 98 1.3 Hi-Jet.
A friend in need is a friend indeed, a friend always in need, an Effin nuisance
When I say loud bang, I mean
When I say loud bang, I mean it's like a bang as if the car has stalled but it doesn't ever stall, just makes this bang and jerks then limp mode then a bang/jerk into 3rd and then back into revving high and limp mode. If you think of being in a dodgem when you hit into another dodgem at the fair ground-same feeling. It's the fact that it comes and goes like it struggles and then the speedo jumps back into life and off we go happy as Larry.. But only for a few kn's and we go back into dead speedo/limp mode. Could this be the transmission computer module?