Hello folks, can you assist me with some information here are the details:
About 4 months ago my transmission was stuck in 2end gear, it only shifts from 1ist to 2end only and goes into neutral, a frind of mine has a scanner which it said it was the P1875 code, "4WD low switch circuit", it has something to do with the 4WD circuit, I could not find the TCCM location, it was supposed to be under the dash, nowhere to be found, I ended up going to GM dealership with the VIN#, they told me that that truck did not had one on, last week I took the truck to a repair shop to have it inspected to see if they could find the problem, they said the transmission needed to be rebuilt for $1,400.00, " I'm able to engage and disengage the 4WD low and hight with no problems, it works fine, any advices somebody might have????
Take it to a better reputable shop.
Here is some information to all and hope it helps. When the VCM detects a continuous open, short to ground or short to power in the 4WD low circuit, then DTC P1875 sets. DTC P1875 is a type B DTC and not a power train issue like ENGINE and TRANSMISSION.
For vehicles equipped with an active transfer case, the four wheel drive (4WD) low circuit consists of the vehicle control module (VCM), a transfer case control module and the circuit wiring. The transfer case control module controls the 4WD low signal on circuit 1694.
When you selects 4WD low, the transfer case control module grounds circuit 1694, and the 4WD low signal voltage on the circuit changes from ignition voltage to zero volts. The VCM then compensates for transfer case gear reduction in the transmission output shaft speed (OSS) sensor signal. The VCM uses the transmission OSS sensor signal to adjust shift points, line pressure and torque converter clutch (TCC) scheduling.
For vehicles not equipped with an active transfer case, the 4WD low circuit consists of the VCM, a transfer case switch and the circuit wiring. The transfer case switch controls the 4WD low signal on circuit 1694.
Once again when you selects 4WD low, the transfer case switch closes and the 4WD low signal voltage on circuit 1694 changes from ignition voltage to zero volts. The VCM then compensates for transfer case gear reduction in the transmission output shaft speed (OSS) sensor signal. The VCM uses the transmission OSS sensor signal to adjust shift points, line pressure and TCC scheduling.
Conditions for Setting the DTC
DTC P1875 sets if one of the following conditions occurs:
Condition 1
• The 4WD low switch is in 4WD low.
• The transfer case is not in 4WD low.
• The TCC slip speed is -3000 to -50 RPM.
• The speed ratio is 0.8-1.2 (the speed ratio is the engine speed divided by the transfer case output speed).
All conditions met for 5 seconds.
Condition 2
• The 4WD low switch is not in 4WD low.
• The transfer case is in 4WD low.
• The TCC is commanded ON.
• The TCC slip speed is 100 to 3000 RPM.
• The speed ratio is 2.5-2.9.
• All conditions met for 10 seconds.
Action Taken When the DTC Sets
The VCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met. When the VCM commands a normal shift pattern (not a 4WD low shift pattern). The VCM records the operating conditions when the Conditions for Setting the DTC are met. The VCM stores this information as Freeze Frame and Failure Records and stores DTC P1875 in VCM history during the second consecutive trip in which the Conditions for Setting the DTC are met.
Conditions for Clearing the MIL/DTC 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, but the VCM clears the DTC from VCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring and cancels the DTC default actions when the fault no longer exists and/or the ignition switch is OFF long enough in order to power down the VCM.
Start with inspecting the wiring at the VCM, the transfer case control module (active transfer case vehicles), the transfer case switch connector (non-active transfer case vehicles) and all other circuit connecting points for the following conditions:
- A backed out terminal
- A damaged terminal
- Reduced terminal tension
- A chafed wire
- A broken wire inside the insulation
- Moisture intrusion
- Corrosion
Good luck and keep us posted, BTW the VCM is located with your ECM and here is a link to a ground update to your VCM is your think that may be the issue
http://chevroletforum.com/forum/sil...walkthrough-vcm-ecu-ground-wire-update-39893/ . Also if you have any P code along with your 1875 Code, it may be the cause of your 1875 code also.
• No TP sensor DTCs P0122, or P0123
• No VSS assembly DTCs P0502 or P0503
• No TCC solenoid valve DTC P0740
• No TCC stuck ON DTC P0742
• No 1-2 SS valve DTC P0751 or P0753
• No 2-3 SS valve DTC P0756 or P0758
• No TFP manual valve position switch DTC P1810
• No TCC PWM solenoid valve DTC P1860
• No transmission component slipping DTC P1870
• The engine speed is greater than 450 RPM for 5 seconds
• The engine is not in fuel cutoff
• The vehicle speed is greater than 11 km/h (7 mph)
• The TP angle is 17-50%
• The engine torque is between 50-400 ft lbs
• The engine vacuum is between 0-105 kPa
• The gear range is D4
• The shift solenoid performance counters are zero
• The TFT is 20-130°C (68-266°F)
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Molson02536
