Engine speed signal

[bean52777]

Does anyone know whether the ECU get the engine speed signal from the cam sensor or crank sensor during cranking? Does it use the signal from one during certain conditions and the other during other conditions?

I'm trying to diagnose the P0740 TCC lockup fault I am getting on my 2002 XC70. The transmission shifts like a dream and only throws the code after the transmission is warmed up and when driving at freeway speeds (usually during a slight hill climb). I have flushed the fluid, use a magnefine filter, and added an additional transmission oil cooler. The same problem existed before and remained after doing/adding all of those items. I can clear the fault while driving to get it out of limp mode.

Since the code is due to a detected speed discrepancy between engine RPM and Transmission speed, and all shifting is otherwise perfect, I'm looking at a possible issue with the engine speed signal being used. Another crazy symptom is that I can drive for hours on the freeway in cruise and have no problems. When I pull it out of cruise at freeway speeds, I get the fault. Is the system relying on a different sensor for engine speed when in cruise as opposed to what it uses when not in cruise.

I also have an extended cranking issue that I'm starting to think may be related. The engine often has an extended crank that sometimes acts like the timing is off. It always starts, but only after a 2 or 3 second crank. It really acts like the timing is off. Once it starts, everything is fine. The extended cranking is worse after a hot soak (drive go into a store and try and start again). This leads me to believe the crank or cam sensor may be buggy. Which one is the ECU using during cranking?

[pelagikos]

I started getting converter lockup related code when I had about 105 -110 kmiles on the odometer. Otherwise it was shifting fine.

Software upgrade took care of the issue.
The code was different though, but then it is different model year...TCM-002F

[JRL]

Bad torque converter

[bean52777]

I started getting converter lockup related code when I had about 105 -110 kmiles on the odometer. Otherwise it was shifting fine.

Software upgrade took care of the issue.
The code was different though, but then it is different model year...TCM-002F

I believe tcm-002f is the same as p0740.

[vtl]

Could be a sticky/worn SLU solenoid (controls TC lockup function) or leaky valve body. TC can be bad too, but check VB in a reputable transmission shop first.

[bean52777]

Transmission was rebuilt 40k ago, but I haven't completely ruled out the solenoids or VB having issues. I'm just puzzled as to why I have no problems in cruise.

Anybody have any ideas as to why there are no problems when the cruise control is set? I have a test section of freeway where I can get it to throw the fault consistently. It is a slight incline where I am humming steadily along at 55mph. Everytime I drive it without cruise set, I get the faultand the trtansmission goes into limp mode. When I drive the same section in cruise, there are no faults and no problems.

Theories?

[pelagikos]

Two dealers independently of each other told me I needed a new transmission.
A independent shop suggested new software - problem solved. 5 years now.
Simptoms were that the transmission rarely and randomly would go into safe mode while going from acceleration to coasting upon entering freeways.

The transmission software that was throwing the safe mode and code was from summer 2002. Maybe you got same version.

[bean52777]

Two dealers independently of each other told me I needed a new transmission.
A independent shop suggested new software - problem solved. 5 years now.
Simptoms were that the transmission rarely and randomly would go into safe mode while going from acceleration to coasting upon entering freeways.

The transmission software that was throwing the safe mode and code was from summer 2002. Maybe you got same version.

Good to know. I'll take it into an independent shop near my house and see what they can do.

[bean52777]

Solved!
I cleaned the throttle plate in the ETM and I no longer get the TCC lockup fault.

That explains the reason it had no problem when cruise control was set.

[kutcht1]

Nice follow-up and fix!
This is good info and will I am sure help others from a bad experience with a transmission issue which was NOT a transmission or torque converter issue at all.
TomK