P0218 low fluid?

Mogman

Member
May 3, 2020
173
4
18
Papalote, TX
I am chasing a P0218 high transmission fluid code, If I clear it, it comes back right away (stone cold) and I have not observed the fluid from the cooler any higher than 160 deg. so far in my very limited testing of this conversion.
I see that one of the causes can be low fluid, I understand how low fluid can cause an over temp issue but is it possible that low fluid alone can cause the code?
I am having some concerns about the accuracy of my dipstick and have not found any way to "calibrate" the dip stick like can be done with say the TH400 which is full at the gasket surface.
I just want to eliminate the possibility that low fluid alone can cause the code before I start tracing out the TCM temp circuit (as in they combined low fluid with high temp) This is a stand alone installation and the donor was wrecked rather severely so I have already found and repaired one wire pulled out of the TCM plug.
THANKS!!
 
Last edited:

Mike L.

Got Sheep?
Staff member
Vendor/Sponsor
Aug 12, 2006
15,492
126
63
Disneyland, CA
Simple
Buy a filler tube and matching dip stick for any 5 or 6 speed Allison. Cases are all the same.
 

Mogman

Member
May 3, 2020
173
4
18
Papalote, TX
I am measuring 20K ohms from the TCM pin 54 (TFT sensor) to ground, anyone know if that is in the ballpark for a room temp. trans.
EDIT, found a ohms list, according to that list 20K should be about 5 deg F so I definitely should not be getting a high temp code.
 
Last edited:

2004LB7

Well-known member
Dec 15, 2010
3,183
168
63
Norcal
I am measuring 20K ohms from the TCM pin 54 (TFT sensor) to ground, anyone know if that is in the ballpark for a room temp. trans.
EDIT, found a ohms list, according to that list 20K should be about 5 deg F so I definitely should not be getting a high temp code.
Thermistors temp to ohms range is not linier. You can't assume the higher temp range is good when your reading is that far off from the chart on the low end. Either test it at a higher temp such as boiling water or just put a new one in
 

Mogman

Member
May 3, 2020
173
4
18
Papalote, TX
Thermistors temp to ohms range is not linier. You can't assume the higher temp range is good when your reading is that far off from the chart on the low end. Either test it at a higher temp such as boiling water or just put a new one in
As I see it the higher end means nothing, I am getting an over-temp code at room temperature, according to the ohm meter the TCM should think the temp is 5 deg F, not saying it does not need a new temp sensor it just seems unlikely that is why I am getting a high temp code at room temperature, I am thinking it may be a bad TCM
 

2004LB7

Well-known member
Dec 15, 2010
3,183
168
63
Norcal
I see. Make sure the harness is not shorted out. Either together or to ground. If it is a negative coefficient thermistor (Judging buy your measurement of 20kohms and 5° it would likely be) then a short would make the TCM think the tamp was high. Maybe take some meter readings from the TCM connector to see what resistance the TCM would see. Measure from wire to wire and wire to ground
 

testdrive

Member
May 28, 2013
64
1
8
Just for conversation sake measure the engine temp sender voltage at it terminal. Would guess the two sensors might share similar readings when at the same approx temp. Those senders are biased with 5 volts and the thermistor simply pulls that toward ground somewhat depending on the temp and resistance.
This is an assumption and you may know the meaning of that.;)
 

Mogman

Member
May 3, 2020
173
4
18
Papalote, TX
I see. Make sure the harness is not shorted out. Either together or to ground. If it is a negative coefficient thermistor (Judging buy your measurement of 20kohms and 5° it would likely be) then a short would make the TCM think the tamp was high. Maybe take some meter readings from the TCM connector to see what resistance the TCM would see. Measure from wire to wire and wire to ground
The measurement was taken at the TCM connector so that would include all of the harness.
 

Mogman

Member
May 3, 2020
173
4
18
Papalote, TX
Just for conversation sake measure the engine temp sender voltage at it terminal. Would guess the two sensors might share similar readings when at the same approx temp. Those senders are biased with 5 volts and the thermistor simply pulls that toward ground somewhat depending on the temp and resistance.
This is an assumption and you may know the meaning of that.;)
Good point, could be the pull up resistor in the TCM is open
 

Mogman

Member
May 3, 2020
173
4
18
Papalote, TX
OK,,, I was reading the plug upside down, damn things are too symmetrical. pays to take the cover off of the plug and confirm wire color (which I had to do to get the voltage reading) ANYHOO,,, pin 54 the TFT sensor lead reads 2.6K ohms to ground which is pretty damn close to the chart for the 77 deg this morning, and powered up I get 3.3V which should be right in line with the correct reading, So I can only conclude the TCM is bad, I have one coming, was supposed to be here today but it looks doubtful.
I am no stranger to SCADA but the automotive end is new, I will learn how to read the plugs etc. as I go, getting there....
 
Last edited:

Mogman

Member
May 3, 2020
173
4
18
Papalote, TX
50 bucks for both is not expensive.
Not terribly expensive but could not use it for anything but a reference then toss it away, someday somebody might have the pan off of a transmission and simply give me the measurement from the bottom of the tube to the tip of the dipstick.
 

Animals1234

Member
Jun 8, 2017
33
2
8
Did your problem ever get solved? I'm not much of an electrical guy or understand the terms but I had a similar code come up on my truck. I swapped the tcm and it fixed my issue. It was on '03 LB7.
 

Mogman

Member
May 3, 2020
173
4
18
Papalote, TX
Well I was also getting a P0090 FPR open and a U0073 communications bus off, I finally dug down far enough in the engine to repair the open harness to the FPR and now the only codes I see are U0140 and U0121 which have to do with BCM and traction control, I have U0140 set to "not reporting, no MIL" in the ECM, do not see U0121 in the ECM DTCs and both are reported as TCM codes, but I do not see any DTC codes in the TCM tune, I think am going to re-post in a more appropriate forum.
Strange how a FPR issue seemed to be causing the high trans. temp and communications buss codes...
 
  • Like
Reactions: mohlerd

Mogman

Member
May 3, 2020
173
4
18
Papalote, TX
Took it out for a little test drive and came back with a whole pile of codes, U0073, U0121, U0140, P0880, P2536, P0218.
I am just going to have to wait until the TCM gets here on Tue, (I hope)
 

Users Who Are Viewing This Thread (Users: 0, Guests: 1)