Transmission code reader

[Cougar_Jon]

My 94 XJ40 's transmission has gone into limp mode. Took it to the best shop available and they are having no luck. Have checked the firewall relay and fluid levels, no luck. The shop keeps focusing on failure codes for my ZF4HP24. But they don’t have a compatible reader. When I do a search at say Ebay I am over whelmed by volume. Can anyone with experience recommend brand & model that will serve my requirements. Thanks, John Meade

[Bryan_N]

Jon,

I doubt very much that the problem is in the transmission itself. Over the years there have been many reports of the car going in to ‘limp home mode’ and I do not recall any being due to a faulty transmission unit.To get a flavour of the sort of problems encountered enter ‘Limp Mode XJ40’ in the archive search engine facility. There are pages of posts on the subject - this being typical -

[xj40] Transmission Limp Mode - can't find the cause

Good day Gents! About 2-3 months ago, my car started going in limp mode. It would sometimes go away with stopping the car and simply restarting. Other times it would not go away at all. The transmission appears to have enough fluid. It looks to be towards the max level when warm. I do not know when the last fluid & filter change was. I cleaned the throttle body in December of 2009. The problems didn’t start until 2010. About a month ago, I drilled a hole in the Throttle Position Sensor…

A favourite suspect after the firewall relays seems to be an oil soaked TPS.

I believe Bob Gauf’s post answers your question about a code reader for these cars.

[Joe77 (Joseph)]

Jon, years ago I opened up the transmission control module (TCM) and found a cracked solder joint where a relay ( yes, there’s a relay in there) is soldered to the pcb. My car ('94 MY) also went into limp home mode intermittently so it can be one of the cause. Worth checking it.