#P1859 Transmission component slipping Transmission is in 4th gear with TCC engaged and the ECM has detected excessive slippage when comparing the input shaft speed to the output shaft speed. Probable cause: Trailer towing may set code Check transmission fluid level Internal transmission fault

The powertrain control module (PCM) monitors the difference between engine speed and transmission output speed. In D3 drive range with the TCC engaged, the engine speed should closely match the transmission output speed. In D4 drive range, with the TCC engaged, the TCC slip speed should be -20 to +50 RPM.
When the PCM detects excessive TCC slip when the TCC should be engaged, then DTC P0894 sets. DTC P0894 is a type B DTC.

TCC - torque converter clutch
Diagnostic Aids
• Bronze material found in the transmission oil pan may indicate stator shaft bushing wear. If bushing wear is suspected, inspect the stator shaft and the input, turbine, shaft for damage.
• Refer to Symptoms - Automatic Transmission for more information.
Do you have a scan tool ?

Install a scan tool.
Turn ON the ignition, with the engine OFF.
Important: Before clearing the DTC, use the scan tool in order to record the Freeze Frame and Failure Records. Using the Clear Info function erases the Freeze Frame and Failure Records from the PCM.
Record the DTC Freeze Frame and Failure Records.
Clear the DTC.
Important: It may be necessary to allow multiple TCC cycles to occur in order to verify a slipping condition. It may also be necessary to ensure the transmission is warm before performing this step.
Drive the vehicle in 4th gear with the TCC commanded ON.
Does the scan tool TCC Slip Speed measure within the specified range for 7 seconds?
130-800 RPM

Inspect the torque converter clutch (TCC) solenoid valve for the following conditions:
• Internal malfunction, such as sediment or damage
• Damaged seals
• Refer to Torque Converter Clutch Pulse Width Modulation Solenoid, Torque Converter Clutch Solenoid, and Wiring Harness .
Inspect the torque converter clutch pulse width modulation (TCC PWM) solenoid valve for the following conditions:
• Internal malfunction, such as sediment or damage
• Damaged seals
• Refer to Torque Converter Clutch Pulse Width Modulation Solenoid, Torque Converter Clutch Solenoid, and Wiring Harness .
Did you find and correct the condition?

P0741 ** TCC, internal components TCC slippage detected The PCM picked up an excessive amount of slippage during normal vehicle operation. TCC slippage/erratic or no torque converter clutch operation. Flashing Transmission Control Indicator Lamp (TCIL).
Refer to Diagnosis By Symptom in this section.

P1870 ! not P01870
DTC P1870 Transmission Component Slipping (Buick Built Before 6/17/97)
DTC P1870 Transmission Component Slipping (All Other Applications)
Circuit Description
The Powertrain Control Module (PCM) monitors the Torque Converter Clutch (TCC) slip by calculating the difference between the engine speed and the transmission output shaft speed.
If the PCM detects an excessive amount of slip when the TCC is engaged, then DTC P1870 sets. DTC P1870 is a type B DTC.

DTC P0894 Transmission Component Slipping
DTC P0894Circuit Description with 4L80-E / 4L85-E Automatic Transmission The powertrain control module monitors the engine speed and the transmission output shaft speed. The PCM calculates turbine shaft speed and torque converter clutch (TCC) slip speed by using inputs from the automatic transmission input shaft speed sensor, automatic transmission output shaft speed sensor, and other transmission components. The forward clutch housing is used as the AT ISS rotor. Whenever the TCC is engaged, engine speed and turbine speed will closely match, indicating low TCC slip speed. In D3, with the TCC engaged, calculated transmission component slip can only occur in the torque converter. In D4 OVERDRIVE, with the TCC engaged, transmission component slip can occur in the TCC or the fourth clutch assembly. If the PCM detects an excessive TCC slip speed in D4 OVERDRIVE, when the TCC should be engaged, then DTC P0894 sets. DTC P0894 is a type C DTC. For California emissions vehicles, DTC P0894 is a type B DTC.DTC Descriptor This diagnostic procedure supports the following DTC: DTC No MAF sensor DTC P0101, P0102 or P0103. No MAP sensor DTC P0106, P0107 or P0108. No TP sensor DTC P0120 or P0220. No VSS DTC P0502 or P0503. No ISS DTC P0716 or P0717. No TCC Stuck Off DTC P0741. No TCC Stuck On DTC P0742. No 1-2 SS valve DTC P0751, P0752 or P0753. No 2-3 SS valve DTC P0756, P0757 or P0758. No TFP manual valve position switch DTC P1810. No TCC PWM solenoid valve DTC P2761. The throttle angle is 10-100 percent. Engine speed is 1,250-5,000 RPM. The TFT is Vehicle speed is TFP manual valve position switch indicates D4. The TCC is commanded ON for 0.04 second or greater. TCC is locked ON for greater than 0.1 second. Commanded The PCM detects slip in the torque converter clutch and/or the fourth gear clutch pack with the TCC in an apply or locked mode. DTC P0894 sets during the second consecutive trip when one of the following conditions occur: The TCC slip speed is 100-550 for 10 seconds for three occurrences.The TCC slip speed is 100-550 for 10 seconds, the PCM commands maximum line pressure. The TCC slip speed is 100-550 for 12.5 seconds, the PCM commands the TCC Off for 2 seconds. The TCC slip speed is 100-550 for 15 sec For California emission equipped vehicles, the PCM illuminates the malfunction indicator lamp during the second consecutive trip in which the Conditions for Setting the DTC are met. For Federal emission equipped vehicles, the MIL is not illuminated. The PCM commands maximum line pressure. The PCM inhibits the TCC engagement. The PCM freezes transmission adaptive functions. The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Freeze Frame, California only, and Failure Records, California and Federal. The PCM stores the DTC P0894 in PCM history during the second consecutive trip, California, or the first trip, Federal, in which the Conditions for Setting the DTC are met. For California emissions, the PCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes. A scan tool can clear the MIL/DTC. For California emissions, the PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without an emission related diagnostic fault occurring. For Federal emissions, the PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without a non-emission related diagnostic fault occurring. The PCM cancels the DTC default actions when the fault no longer exists and the ignition switch is OFF long enough in order to power down the PCM. A TFP manual valve position switch malfunction can set DTC P0894. A mechanical failure of the shift solenoids or TCC PWM solenoid valve can set DTC P0894. Internal transmission failures can result in a DTC P0894. Sticking or contaminated shift valves may cause intermittent slipping in D4. DTC P0894 defaults to an elevated line pressure condition which may result in partial TCC apply. This may produce an idle surge that could stall the engine. The numbers below refer to the step numbers on the diagnostic table. 3. This step tests the indicated range signal to the actual selected range. A faulty TFP manual valve position switch can set a DTC P0894. 4. This step tests for excessive TCC slip speed while in a commanded TCC lock-up state and in fourth gear; and confirms that the fault is present. 5. This step tests for excessive TCC slip speed while in a commanded TCC lock-up state and in third gear. 6. This step tests for a sticking TCC shift valve. 7. This step tests for proper transmission line pressure.

Here is the definition of the code.
I doubt replacing an electrical component would do it.

P1870 CHEVROLET Description Transmission is in 4th gear with Torque Converter Clutch (TCC) engaged and the Engine Control Moduel (ECM) has detected excessive slippage when comparing the input shaft speed to the output shaft speed
Read more: http://engine-codes.com/p1870_chevrolet.html#ixzz26gqhKHvr

P1870 CHEVROLET Description Transmission is in 4th gear with Torque Converter Clutch (TCC) engaged and the Engine Control Moduel (ECM) has detected excessive slippage when comparing the input shaft speed to the output shaft speed Causes could include fluid problems and damaged clutches.

Read more: http://engine-codes.com/p1870_chevrolet.html#ixzz21kpJ6kDL

P0734=A/T 4th gear incorrect ratio. This has nothing to do with the speed sensor. If the speed sensor was faulty, it would also set OTHER gear incorrect ratio codes. My experience tells me the 4th gear incorrect ration indicates the torque converter clutch (TCC) is slipping and nothing more. Unless there was a speed sensor DTC (Diagnostic Trouble Code), the sensor is not the issue (yet). The fact P0734 was set (trust the computer), the TCC is slipping (out of range). Question: Maintenance history may indicate the wrong transmission fluid may have been introduced. Hyundai's Transmission fluid is strictly SPIII... there is no substitute. The incorrect fluid will cause 4th gear slippage. Now, having said that, it doesn't mean the 4th gear (lock-up) clutch isn't worn out. Have a qualified/certified Hyundai Service Technician properly diagnose this issue.

U are going to need to overhaul the transmission here, the smoke is the trans overheating from excessive slippage i suspect.code for wrong gear ratio's mean the input and output shaft speed are out of symc for the gear the trans is in, the 3rd or 4th gear is the usual codes, this sometimes is caused by defective speed sensors but most times the trans is slipping and the TCM detects that and sets a code

I recently ran into this same problem. My truck has 125,000 miles. The service engine light would come on from time to time. I did as you and got a P1870 code.

P1870
The transmission is in 4th gear with the TCC (torque converter clutch) engaged and the ECM has detected excessive slippage when comparing the input shaft speed to the output shaft speed.

Probable causes

1. Towing a trailer.
2. Transmission fluid level.
3. Internal transmission failure.

In my particular case a fluid and filter change solved the problem. I do plan on dropping by the trans shop and let them do a complete service in the near future. (Fluid, filter, band adjust, and check pressure)

Good Luck.
Bob