|Code||Fault Location||Probable Cause|
|P0770|| Shift solenoid (SS) E -circuit malfunction |
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|Wiring, shift solenoid, ECM/PCM!TCM|
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What Does Code P0770 Mean?
OBD II fault code P0770 is a generic code that is defined as “Shift solenoid (SS) E -circuit malfunction”, and is set when the PCM (Powertrain Control Module) detects a failure of, or malfunction in, the control circuit of the shift solenoid in the transmission that is labelled “E”. Note that the shift solenoid labelled “E” itself forms part of the affected control circuit.
NOTE: While this code typically refers to the solenoid and the control circuit that controls the torque converter lock-up clutch, car manufacturers do not always label circuits, sensors, parts, and components in the same way. Therefore, it is necessary to refer to the manual for the affected application to determine which transmission shift solenoid/circuit is labelled “E” on that application. Failure to identify parts, sensors, and circuits correctly could lead to a misdiagnosis, and the unnecessary replacement of parts and components.
All automatic transmissions use varying degrees of hydraulic pressure to engage/disengage various transmission components such as clutch packs and the torque converter lock-up clutch in order to accomplish gear shifts.
To make gear shifts comfortable and efficient, the PCM/TCM controls a series of pressure control solenoids to redirect pressurized transmission fluid from one circuit to another, based on input data from a variety of engine and driveability sensors. This process is roughly analogous to the way different gears are decoupled and engaged in different combinations in manual transmissions to bring about different gear ratios.
However, in automatic transmissions the process of establishing different gear ratios smoothly and reliably depends on how efficiently pressurized fluid is channelled between hydraulic circuits in order to engage/disengage clutch packs and other components. Thus, should one pressure control solenoid (or its control circuit) fail, one gear ratio cannot be disengaged or “deselected” before the next ratio is selected, since the flow of pressurized fluid cannot be controlled effectively.
Note however, that on applications where code P0770 refers to the torque converter lock-up clutch, gearshifts may still be possible, albeit at reduced engine power since the PCM/TCM may initiate a failsafe or limp mode both as a safety measure, and to prevent possible damage to the transmission.
Nonetheless, when code P0770 is set, the PCM/TCM will recognize that it can no longer control the flow of pressurized transmission fluid effectively, and on most applications, a warning light will also be illuminated.
Where is the P0770 sensor located?
The image above shows a typical automatic transmission valve body, with all the shift solenoids fitted along one (the left) side. However, while this arrangement is common, it is not representative of how shift solenoids are arranged on all transmissions; in fact, on some transmissions, some shift solenoids are actually located outside of the transmission.
Nonetheless, regardless of how and where the shift solenoids are arranged on any given transmission, it is critically important to refer to the manual for the affected application to locate and identify shift solenoid “E” correctly. Failure to do so will not only result in a misdiagnosis, but also in the distinct possibility that severe damage to the transmission could occur.
What are the common causes of code P0770 ?
Note that while dirty/degraded/contaminated transmission fluid, a clogged transmission fluid filter, or a defective transmission pressure pump can cause a wide variety of transmission problems, these issues rarely cause failures of, or malfunctions in the control circuits of transmission shift solenoids. However, if a defect in the transmission’s internal harness is found, the better option is to replace the entire internal harness to prevent a recurrence of this code. Keeping this in mind, some common causes of code P0770 could include the following-
- Damaged, burnt, shorted, disconnected, or corroded wiring and or connectors
- Defective pressure control solenoid “E”
- Defective valve body
- Failed or failing PCM/TCM. Note that this is a rare event and the fault must be sought elsewhere before any control module is replaced