Gearbox in Limp Mode

[Nezza42]

For the last couple of days, my gearbox (AF23 in my 2.2 Vec) keeps going into limp mode after only a few miles.

I've got an amber engine warning in lower right corner of dash (hand book says it's the warning for the exhaust gasses ), but no engine symbol with the spanner through in the centre of the dash!


In limp mode, I get 2nd & 5th in manual, though the change between the two is very, very harsh, so I'm leaving it in D, which only gives 5th.

When the car 1st starts, the gearbox runs perfectly. All changes are smooth, etc. Cruise works, all's right with the world. Then suddenly, it drops into limp & Cruise disappears.

I'm waiting on the delivery of a bluetooth OBD2 reader, so don't yet know what the fault code is.

As the box works perfectly until limp mode, is it likely to be something (relatively) simple, like a sensor / ecu?

Anyone had a similar experience?

Cheers, Nez

[Vectra Meldrew]

Have you checked the fluid level of the gearbox? Not sure if the AF23 has a dipstick or not.

[Nezza42]

No, so far I've had no time to look at it. I'll check it this w/e. I'll also check whatever sensors/connectors I can find are securely plugged in.

Hopefully the OBD2 reader will arrive today, so I can at least get the fault code.

Confused why the manual says the engine light I'm showing is exhaust gas & not the general engine fault light with spanner though????

[Nezza42]

OK, got my OBD2 reader & the fault code is P0720, which I believe is "Output Speed Sensor Circuit Malfunction"

Checked the connection & that appears fine. Have cleared the fault code, & the engine light has gone, so later I'll take it for a spin & wait for the fault to reoccur & check the code again.


Any ideas what may be causing the this fault? Is it likely to be the sensor or the wiring or the ECU (TCM?)

[jonnybravo]

Hi Nezza,it's probably a faulty input/output speed sensor due to moisture inside sensor,VX fit new sensor and coat sensor with grease to prevent moisture ingress.sensor part no 93173888

[Nezza42]

That's what I'm hoping!

According toVx, the input & output sensors are the same, so I'm going to swap them this weekend and see if the fault code changes to one for fhe input sensor. This should confirm if the sensor itself is u/s. If the code's the same, then the fault must lie elsewhere.

Cheers, Nez

[benny]

The code and fault you talk of is normally due to water in the oil from the oil cooler pipe seals if this is the case flush the oil and replace change the seals .. If the fault returns your going to need a new gearbox or yours overhauling ....

[Nezza42]

Update......

Checked oil on dipstick & it looks a brownish purplish colour, not particularly viscous and not at all creamy or milky.

Swapped the input & output sensors around & immediately the box felt different. Still went into limp mode after a short drive, but the changes didn't feel as smooth as they did before the swap, so something's changed.

The fault light hasn't come back on yet, but my obd2 code reader is showing a pending fault code P0715.

As this is "Input/Turbine Speed Sensor Circuit Malfunction" where as the original fault was "Output Speed Sensor Circuit Malfunction" this would suggest it's the sensor that's at fault

So, new sensor will be ordered on Monday!

Fingers Crossed!!!!!!

[Nezza42]

New sensor fitted & all seems well!

Cleared fault codes & driven around town for a while, checked for any pending fault codes & none showing, so hopefully, it's sorted.

I'm gonna get the ATF flushed & get the pan cleaned & filter replaced. Should be able to check for signs of any contamination at the same time.

Will also look at how much it'll cost to get the cooling system modded.

Nez

[Nezza42]

******! Fault is back

It seems as though the car is inducing the output sensor to fail........is this possible????