Question about 2005 GMC Sierra 2500HD 4WD

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Engine code 894

Driving 25 mph and engine light come on, and it shifted hard.

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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.

Posted on Apr 22, 2014

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1 Answer

Transmission shifts hard


You don't give me much information to work with. However, 1st, look at the engine mounts. You may have a broken mount. This will make it feel like the transmission is shifting hard. Other than that, there is only a few things that will cause this. The speed sensor tells the computer when to shift the shift solenoids. It may not be "seeing" a quality signal. If this is the case, the speedometer will be bouncing too. Last idea is that it is skipping a gear. Starts in 1st, should go to 2nd at about 10 MPH. 3rd at 25 to 30 MPH. And, if you have a Overdrive transmission, it should go into overdrive at around 45 to 55 MPH. If it is skipping 2nd, it will engage 3rd at a high engine speed, and will feel like a sudden slam into gear. If this is true, your transmission needs some work. Hope this all helps. Good Luck.

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    • 1 Start your Dodge truck's engine.
    • 2 Turn the electronic transfer case from "2WD" to "4WD Lock" to engage the high range 4WD, if the dodge truck is equipped with an electronic transfer case; otherwise, shift the transfer case lever from "2H" to "4H." The electronic transfer case is located on the instrument panel and is marked with "2WD," "4WD Lock" and 4WD Low." The lever-equipped transfer case is located to the right of your leg and is marked with "2H," "4H" and "4L."
    • 3 Shift the transmission into "Neutral" while the vehicle is either stopped or rolling at 2 to 3 mph to begin engaging in the low range 4WD. Turn the electronic transfer case to "4WD Low," if the Dodge truck is equipped with an electronic transfer case; otherwise, shift the transfer case lever from "2H" or "4H" to "4L."
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    • Indicator lights will come on and alert you that your vehicle is in either the high or low range of 4WD.
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    • Many Dodge trucks allow you to shift from 2-wheel drive to the high range of 4WD at up to 55 mph--consult your truck's manual to ensure that this is possible. Do not exceed 55 mph while engaged in the high range of 4WD. Do not exceed 25 mph while engaged in the low range of 4WD.
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1 Answer

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You have a trans issue, have the system self tested for codes, Kragen auto and others do this for free. Get back to me with the trouble codes.

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