OBDii Scan Port Issue

[Kieran76]

So i've been trying to use a scan tool on my grand voyager 2.8 crd lx and it doesnt connect to the ecu so i cant get any readings. I have since spent days researching this issue and i have found one small section in a repair manual that states that 2003-2007 grand/voyagers OBDii ports can become disabled if the temperature is outside of the battery temperatures high and low range. Unfortunately, one of the dashboards error codes refers to the PCM battery temperature sensor as not working, so i cannot test if this is true or not. I have ordered a new sensor and will check it once the part arrives. In the meantime, has anyone come across this? Is it true? I will update on my progress once i find the fix.

[RichardM]

Mk4 is not fully OBD compliant,  J1850 protocol is implemented for some functions but very few readers work, even fewer allow you to reprogram anything..

The battery temperature sensor is also used for

OBD II diagnostics. Certain faults and OBD II monitors are either enabled or disabled depending upon the battery temperature sensor input (example: disable purge and EGR, enable LDP).

Most OBD II monitors are disabled below 20°F.

 

The battery temp is read via a NTC thermistor  readings are;

SPECIFICATIONS - BATTERY TEMPERATURE SENSOR

°C °F K-Ohms Min. K-Ohms Max.

-40 -40 291.4 381.7

-20 - 4 85.8 108.4

20 68 11.4 13.6

25 77 9.1 10.9

120 248 0.37 0.41

130 266 0.28 0.32

to bypass if you cannot get a replacement thermistor replace it with a 12K resistor (20sih  degrees C.

Any mention of diagnosis in the manual refers to the DRBIII reader - obsolete 2nd hand rare and blxxdy expensive.

[Kieran76]

Managed to bypass it today, i used a heat sensor i had from an electronics kit, used a cheapy obd scanner and it read all my transmission errors, much better than the onboard diagnostics which only gave the wonderful p0700 generic code, got all the codes and ordered some new parts, solenoid pack, filter kit, TCU, re-programmer which will be fun to try out, both speed sensors and battery temp sensor. So far bargin prices. Hopefully no replacing the transmission (fingers crossed)now just the aft to buy, so annoying that its so expensive. Will pass on any re-programing info/issues as time goes on, and i might even try out the updated performance enhanced firmware. But one step at a time. I'll be happy with just being able to drive forwards again..lol

[Sergejs]

Congratulations! Which App have you used with obd scanner? Speed sensors most probably not at fault. If your problem would be solenoid pack, speed 2 and R would still be there. Any metal particles in the oil pan? 

[Kieran76]

its a cabled generic scanner, bought it on aliexpress, 25 euro thing. Have found out from mopar that all forward gears can stop working if solenoid pack is faulty. Haven't started to do any draining yet, dreading looking at the pan, have sampled to fluid, black/metalic look to it and doesnt smell great, explains why the solenoid code came up. For now im just waiting on all parts to arrive first. But i have the speed sensors as part of the filter kit so will change them regardless. Has been a nightmare trying to get the atf+4 in spain, its almost unheard of, so might be a clue in that as i doubt it has the right fluid to start with, and here in spain there are many places adverting dexron vi and various atf iii as being compatible, some even list for 40te/41te. Luckily i just searched every listed fluid on the Chrysler registered list. Only 1 available, so played it safe and ordered direct from the manufacturer. Still, ive learned its time consuming and parts are expensive, so if you see something going cheap, buy it quickly, even if you dont need it..lol

 

[Sergejs]

If you have lost all your gears, including R, oil is black with burned smell - most probably torque converter is gone. Have been there...

[bignev]

I've got my fingers crossed that a fluid change helps you!

As, from my own experience, even with NO communication to the Transmission Control Module, I still had 2nd and reverse gears.