Error Code 31

jase_93t · 11th November 2010, 10:04 AM

Hi all

Apologies up front for the long post, but Im in a bit of a pickle......

Car is 1993 Supra Single turbo auto and is producing error code 31, map sensor - abnormal reading.

Ive swapped out the map sensor for another one, reset the engine error code memory, tested the voltage to the map sensor (which I believe is around 5v or so), plugged back in the diagnostic equipment, and it still throwing up the same error code 31.

The car has a very rough idle (cold idle is non-existent, and does have a tendency to cut out if not revved when stationery and generally, really poor fuel consumption/mis-firing under load. Whilst driving, even at low rpm/speeds, any attempt to even moderately accelerate produces hesitancy and mis-fire, and the red master warning light (red triangle/exclamation mark) flashes up on and off until one backs off on the accelerator.

Im going to reduce the fuel pressure via the aeromotive fpr to see if that smoothens things out a bit. Its running stock-ecu with apexi neo s-afc controlling the air/fuel mix.

Plugs are brand new and correctly installed, compression test checks out perfect. However, the car is using the original coil packs - could these be worn out causing such symptoms?

The car used to drive perfect until I took it into a garage to sort out a heater problem (it was blowing the heater fuse), which is now fixed. Could the fixing of the heater wiring somehow, I dont know, cause these symptoms ? Ive asked the auto-electrician if he disturbed something he shouldnt have whilst fixing the heater, but he denies breaking anything (!)

If the map sensor is physically OK, and one would assume it is working, what else could be throwing up the error ?

Ive checked on the following website:

http://mkiv.supras.org.nz/techo.htm#ENGINE_CODES

and its showing 3 possible causes. Im ruling out the possibility of the actual map sensor being the culprit as it seems to check out OK.

Ive checked online for some wiring diagrams to the stock ecu, and there does seem to be a connection for the heater.

I dont want to go through the expense of buying new coil packs / ecu / map sensors purely as a process of elimination when the problem could be more related to wiring than hardware.

Any help much appreciated

Martin F · 11th November 2010, 10:39 PM

Do you have a FCD ?

11th November 2010, 10:04 AM	#1
jase_93t HKS Single Turbo User Jap Spec RZ - Auto (TT) Join Date: Nov 2006 Location: UK Posts: 8	Error Code 31 Hi all Apologies up front for the long post, but Im in a bit of a pickle...... Car is 1993 Supra Single turbo auto and is producing error code 31, map sensor - abnormal reading. Ive swapped out the map sensor for another one, reset the engine error code memory, tested the voltage to the map sensor (which I believe is around 5v or so), plugged back in the diagnostic equipment, and it still throwing up the same error code 31. The car has a very rough idle (cold idle is non-existent, and does have a tendency to cut out if not revved when stationery and generally, really poor fuel consumption/mis-firing under load. Whilst driving, even at low rpm/speeds, any attempt to even moderately accelerate produces hesitancy and mis-fire, and the red master warning light (red triangle/exclamation mark) flashes up on and off until one backs off on the accelerator. Im going to reduce the fuel pressure via the aeromotive fpr to see if that smoothens things out a bit. Its running stock-ecu with apexi neo s-afc controlling the air/fuel mix. Plugs are brand new and correctly installed, compression test checks out perfect. However, the car is using the original coil packs - could these be worn out causing such symptoms? The car used to drive perfect until I took it into a garage to sort out a heater problem (it was blowing the heater fuse), which is now fixed. Could the fixing of the heater wiring somehow, I dont know, cause these symptoms ? Ive asked the auto-electrician if he disturbed something he shouldnt have whilst fixing the heater, but he denies breaking anything (!) If the map sensor is physically OK, and one would assume it is working, what else could be throwing up the error ? Ive checked on the following website: http://mkiv.supras.org.nz/techo.htm#ENGINE_CODES and its showing 3 possible causes. Im ruling out the possibility of the actual map sensor being the culprit as it seems to check out OK. Ive checked online for some wiring diagrams to the stock ecu, and there does seem to be a connection for the heater. I dont want to go through the expense of buying new coil packs / ecu / map sensors purely as a process of elimination when the problem could be more related to wiring than hardware. Any help much appreciated

11th November 2010, 10:39 PM	#2
Martin F Administrator UK Spec - Manual Join Date: Aug 2003 Location: Essex, UK Posts: 10,226	Do you have a FCD ? __________________ Martin UK6TT + Bits & Bobs 'Remember folks, the inside lane isn't just for Xmas' MSOC FAQ MSOC Members Discounts MSOC Resources

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