Yransmission slipping engine torque causes slippage, engine rpm to increase no increase in speed

P1270 - Engine RPM/Vehicle Speed Limiter Indicates the vehicle has been operated in a manner which caused the engine or vehicle to exceed a calibration limit. The engine rpm and vehicle speed are continuously monitored by the PCM. The DTC is set when the rpm or speed fall out of calibrated range. For additional information on the engine rpm/vehicle speed limiter, refer to Section 1, Electronic Engine Control (EC) System , Powertrain Control Software.

• Wheel slippage (water, ice, mud and snow)
• Excessive engine rpm in Neutral
• Vehicle drive at a high rate of speed

The DTC indicates the vehicle has been operated in a manner which caused the engine or vehicle speed to exceed a calibrated limit.

Diagnose Cooling Fan Clutch On engines with belt-driven cooling fans, a fan clutch is often used to save energy and reduce noise. The fan clutch disengages slows or disengages the engine's cooling fan when extra cooling isn't needed. The fan pulls air through the radiator and air conditioning condenser when the vehicle isn't moving fast enough to provide adequate airflow for cooling. A fan can eat up anywhere from a couple of horsepower up to 12 or 15 hp on a big V8, so by reducing the parasitic horsepower loss on the engine the fan clutch makes a noticeable difference in fuel economy

TWO TYPES OF FAN CLUTCHES basic types of fan clutches: thermal and non-thermal (also called "torque limiting Thermal fan clutches have a temperature-sensitive bimetal coil spring on the front that reacts to temperature changes. When the air coming through the radiator is hot, the spring expands and opens an internal valve that reduces clutch slippage. This causes the fan to spin faster for increased cooling. As the air cools, the spring contracts and closes the valve. This increases the amount of clutch slippage, allowing the fan to slow down and decrease cooling FAN CLUTCH OPERATION

The clutch consists of a fluid coupling filled with a silicone based oil. In the cutaway view at the left, the area between the teeth on the clutch plates is filled with silicone fluid. An internal valve opens and closes a passage between the main fluid cavity and a fluid reservoir. When the passage is open, fluid enters the clutch and makes the fan to turn faster. When the valve is shut, fluid flows back to the reservoir but doesn't return, causing the clutch to slip and the fan to turn more slowly.
The non-thermal (torque limiting) fan clutch doesn't have a temperature sensing capability. It reacts only to speed, slipping to limit maximum fan speed to about 1200 to 2200 rpm depending on the application.

FAN CLUTCH PROBLEMS

A slipping fan clutch is often overlooked as the cause of an engine overheating problem.
As a fan clutch ages, fluid deterioration gradually causes an increase in slippage (about 200 rpm per year). After a number of years of service, the clutch may slip so badly that the fan can't keep up with the cooling needs of the engine and the engine overheats. At this point, replacement is often necessary.
Other signs of fan cluch failure would include any looseness in the clutch (check for fan wobble), or oil streaks radiating outward from the clutch hub.
If the clutch is binding, the fan may not release causing excessive cooling and noise, especially at highway speeds

CHECKING THE FAN CLUTCH

A good clutch should offer a certain amount of resistance when spun by hand (engine off, of course!). But if the fan spins with little resistance (more than 1 to 1-1/2 turns), the fan clutch is slipping too much and needs to be replaced.
If the fan binds, does not turn or offers a lot of resistance, it has seized and also needs to be replaced.
Fan speed can also be checked with an optical tachometer, by marking one of the fan blades with chalk and using a timing light to observe speed changes, and/or listening for changes in fan noise as engine speed changes.
You should also try to wiggle the fan blades by hand. If there is any wobble in the fan, there is a bad bearing in the fan clutch, or a worn bearing on the water pump shaft. A bad water pump bearing will usually cause the water pump to leak and/or make noise, but not always. Remove the fan clutch and see if the play is in the water pump shaft. If it feels tight (no play or wobble), replace the fan clutch.

FAN CLUTCH REPLACEMENT

Many experts say it is a good idea to replace the fan clutch at the same time as the water pump if the water pump has failed. The reason is because both age at about the same rate, so if the water pump has failed, the fan clutch may also fail soon. As as we mentioned earlier, a high mileage fan clutch may be slipping excessively increasing the risk of overheating.
When you buy a replacement fan clutch, make sure you get the same type (thermal or nonthermal) as the original. You can always upgrade from a nonthermal to a more efficient thermal fan clutch, but never the reverse. Or, you can get rid of the fan and clutch altogether and install an aftermarket electric fan kit to cool the radiator.

When the PCM detects 3 occurrences of TCC slip between -20 and +50 RPM for 5 seconds, indicating the TCC is applied, when commanded OFF, then DTC P0742 sets. DTC P0742 is a type B DTC.
The PCM energizes the Torque Converter Clutch Solenoid Valve Assembly (TCC Sol. Valve Assy.) by creating a ground path on circuit 422. When grounded (energized), the valve stops converter signal oil from exhausting. This causes converter signal oil pressure to increase and move the TCC apply valve. The TCC Sol. Valve Assy. de-energizes when the PCM no longer provides a ground path. When de-energized, the valve will exhaust fluid and release the TCC
Diagnostic Aids
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Check for PRNDL DTC P0705. DTC P0705 affects transmission operation. This may set DTC P0742 falsely.

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Inspect the transmission fluid for debris.

DTC P0742 Torque Converter Clutch System Stuck ON Step
Action
Value(s)
Yes
No

1
Was the Powertrain On-Board Diagnostic (OBD) System Check performed?
--
Go to Step 2
Go to Powertrain On Board Diagnostic (OBD) System Check

2
Install the Scan Tool .
With the engine OFF, turn the ignition switch to the RUN position.
Important: Before clearing the DTCs, use the scan tool in order to record the Freeze Frame and Failure Records for reference. The Clear Info function will erase the data. Record the DTC Freeze Frame and Failure Records, then clear the DTC.
Start and run the vehicle.
Select TCC Slip Speed on the scan tool.
With the transmission in D4, drive the vehicle through the 1-2 upshift.
In second gear is the TCC Slip Speed within the range specified?
-20 to +50 RPM
Go to Step 3
Go to Diagnostic Aids

3
Inspect for the following conditions:
The TCC apply valve stuck ON because of sediment or damage.
The TCC Sol. Valve Assy. stuck ON because of sediment or damage. Refer to Control Valve Body Assembly Inspection, in Unit Repair.
Was a condition found and corrected?
--
Go to Step 4
--

4
In order to verify your repair, perform the following procedure:
Using the scan tool, clear DTCs.
Operate the vehicle under the following conditions:
• The gear range is D2, D3 or D4.
• The commanded gear is not 1st.
• The engine speed is greater than 500 RPM for 5 seconds.
• Not in fuel shut off.
• The engine torque is 95-270 N·m (70-200 lb ft).
• The throttle position is 14-50%.
• The PCM commands the TCC OFF.
• The TCC slip speed is 150-2000 RPM for 5 seconds.
• The engine speed is 800-4000 RPM.
• The vehicle speed is 32-112 km/h (20-70 mph).
• The speed ratio is 0.65-1.18.
• The last gear change occurred more than 3 seconds ago.
Select Specific DTC. Enter DTC P0742.
Has the test run and passed?
--
System OK
Begin the diagnosis again. Go to Step 1

P1270 - Engine RPM/Vehicle Speed Limiter Indicates the vehicle has been operated in a manner, which caused the engine or vehicle to exceed a calibration limit. The engine rpm and vehicle speed are continuously monitored and evaluated by the PCM. The DTC is set when the rpm or vehicle speed falls out of a calibrated range. For additional information on the engine rpm/vehicle speed limiter, refer to Section 1, Electronic Engine Control (EC) System , Powertrain Control Software.

• Wheel slippage (water, ice, mud and snow)
• Excessive engine rpm in Neutral or operated in the wrong transmission gear
• Vehicle driven at a high rate of speed

The DTC indicates the vehicle has been operated in a manner, which caused the engine or vehicle speed to exceed a calibrated limit

there should be a torque converter clutch servo/solenoid and it is controlled by a sensor
run the fault codes first

Is the car equipped with the Automatic Transmission?
If so, read on.
Otherwise skip to the end and answer some questions.

POSSIBLE SCENARIO:
I have observed a condition where my car surges slightly when the torque-converter clutch (TCC) cycles between lock and unlock when driving on an uphill grade.
First some basics and history that will explain why the TCC is used.

Engine, Torque Converter, TCC, and Transmission relationship--
The TCC allows for a solid connection between the engine and transmission which allows the input to the transmission to rotate at the same speed as the engine.
Without a TCC, there is slippage between the engine and automatic transmission. The slippage is greatest at low engine RPM. That is what allows the engine to run with the automatic transmission in gear, like when you first shift into gear or stop at a stop sign. When the throttle pedal is depressed, the engine RPM begins to increase and the torque converter begins to slip less and less the more the engine RPM increases. The car moves. But even at cruising speeds the torque converter slips slightly. Engine RPM is greater than transmission input RPM, which is realized as slight decrease in fuel efficiency.
When acceleration is complete and a constant speed is being maintained, the engine power output is reduced to the point where the TCC can engage and eliminate any slippage between the engine and transmission. If the car has a tachometer the engagement of the TCC can be verified when a slight reduction in engine RPM observed without a corresponding change in vehicle speed.
One method used to test the operation of the TCC is as follows:
Find a flat section of road where it is safe to perform the test.
Reach a steady speed and keep the gas pedal depressed with one foot. While observing the tachometer (or listening for an increase in engine RPM), with the other foot depress the brake pedal enough to activate the break light switch but not enough to engage the brakes. When the brake light switch activates, the TCC receives a signal to disengage. With the gas pedal being held steady, release the brake pedal and the engine RPM should decrease when the TCC engages.
Old cars with Automatic Transmissions did not use a TCC. I believe the TCC was put in use in an attempt to increase fuel economy.

MY EXPERIENCE WITH SIMILAR SYMPTOMS
The condition that causes that issue on my car is this:
- A slight uphill grade increases the load on the engine.
The car tends to gradually slow and it is necessary to depress the gas pedal to maintain speed.
- Depressing the throttle pedal (manually, or automatically with cruise control engaged) signals the torque converter clutch to unlock when the load increases slightly. (A more drastic load increase would signal the Transmission to downshift to a lower gear.) The corresponding increase in engine RPM and output is enough to compensate for the reduction in speed. When the vehicle speed, engine RPM, and throttle position stabilize to the point that the TCC will engage and the engine RPM will reduce in correspondence with TCC engagement. Now, if the road conditions have not changed, power output is not enough to maintain vehicle speed. With the increased load caused by full engagement between engine and transmission, and the cycle (surging) repeats itself until the road conditions change.

Does that help?
If not:

QUESTIONS
Please define the symptoms.
What are the road conditions when the surge occurs? (A slight uphill grade?)
What is the frequency of the surge?
Does the engine power output have a noticeable surge?
Is there a speed change related to the surge?
Does the tachometer move up and down with little or no change in vehicle speed?
Are all instrument indication in the normal range?
What else has changed?

Good luck!

The RPM of the engine goes up between shifts or more than the road speed when in a gear.
If the engine RPM is increasing but the road speed is not, the transmission may be slipping.

If the RPM goes up you know you have a transmission that is slipping & needs to come out & be rebuilt. That is a no brainer as they say

Sounds like you need to replace the clutch if the rpm's increase alot and the speed increases a small amount the clutch is starting to have excess slippage. If you go to Autozone web site and search a bit you should be able to find the needed type of transmission fluid and quanity needed.

If you step on the gas and the engine accelerates but the car doesn't then that's slippage.

If you press the brake at a stop while you step on the gas you can determine the stall speed of your torque converter, if the engine revs beyond the stall speed then it's the torque converter clutch, TCC clutch solenoid, or a bad converter. Otherwise you need a professionals help.