P1770
P1770 - Inadequate Element Volume LR
For a complete wiring diagram, refer to.
Theory of Operation
The volumes of the transmission fluid needed to apply the friction elements are continuously monitored and learned for adaptive controls. As the clutch friction material wears, the volume of fluid needed to apply the clutch increases. Certain transmission mechanical problems can cause near-zero learned volumes resulting in setting a DTC. The DTC will usually set with other DTCs, which indicates an internal transmission problem.
• When Monitored: Whenever the engine is running. The LR clutch volume index is updated during a 3-1 or 2-1 manual downshift with throttle angle less than 5 degrees. Transmission temperature must be at least 43° C (110° F).
• Set Condition: When the LR clutch volume index falls less than a calibrated value.
Always perform the pre-diagnostic troubleshooting procedure before proceeding. Refer to => Non-DTC Based Diagnostics. Pre-Diagnostic Troubleshooting Procedure
Test Step 1 - Other DTCs Present
• With the scan tool, check DTCs.
Are there any pressure switch sense circuit DTCs present also?
Yes
• Refer to the transmission category and perform the appropriate symptom.
No
• Go to Test Step 2.
Test Step 2 - Check L/R Clutch Volume Index
• With the scan tool, erase DTCs.
• Start the engine and warm the transmission.
• The TRANS TEMP DEG must be at least 43° C or (110° F) before performing the following steps.
• Drive the vehicle and perform at least ten 3-1 manual downshifts at closed throttle from speeds of about 32 Kmh or 20 mph.
• With the scan tool, read the L/R CL VOL INDEX.
Is the LR CL VOL INDEX less than 20?
Yes
• Go to Test Step 3.
No
• Go to Test Step 5.
Test Step 3 - L/R Clutch Circuit Leaks in the Valve Body
• Turn the ignition OFF to the lock position.
• Remove the transmission oil pan.
• Remove the valve body per the service information.
• Check condition of the L/R accumulator springs.
• Look for possible leak paths into the L/R clutch hydraulics circuit within the valve body.
Were any problems found?
Yes
• Repair as necessary.
• Perform the Transmission Verification Test. Refer to => Non-DTC Based Diagnostics. Transmission Verification Test
No
• Go to Test Step 4.
Test Step 4 - Air Check L/R Clutch Circuits
• Perform an air check on the L/R clutch circuit.
• Watch and listen for L/R clutch piston movement.
Does the L/R piston stroke and return properly?
Yes
• Replace the transmission/TRS solenoid assembly. Refer to. With the scan tool, perform Quick Learn.
• Perform the Transmission Verification Test. Refer to => Non-DTC Based Diagnostics. Transmission Verification Test
No
• Repair internal transmission as necessary. Pay attention to the components related to the L/R clutch. A broken or weak L/R clutch return spring, accumulator spring, and/or dislocated snap ring could cause this problem.
• Perform the Transmission Verification Test. Refer to => Non-DTC Based Diagnostics. Transmission Verification Test
Test Step 5 - Verify PCM Operation
• The TRANS TEMP DEG must be at least 43° C or 110° F before performing the following steps.
• Perform eight learnable starts. A learnable start is defined as follows: Start engine. From a standstill, accelerate lightly to 80 Kmh or 50 mph, then brake lightly to a stop. Turn OFF engine.
• With the scan tool, record the CL VOL INDEX for all clutches
• With the scan tool, perform a battery disconnect.
• With the scan tool, read the CVIs and compare them to the readings recorded before the battery disconnect.
Are any of the CVIs less than 5 or different than before the battery disconnect?
Yes
• Using the schematics as a guide, check the powertrain control module terminals for corrosion, damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems are found, replace and program the PCM. Refer to With the scan tool, perform Quick Learn.
• Perform the Transmission Verification Test. Refer to => Non-DTC Based Diagnostics. Transmission Verification Test
No
• Test Complete.