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DTC DESCRIPTIONSName of Code: P1684(12) - Battery was Disconnected (Info Only)
When Monitored: Whenever the key is in the Run/Start position.
Set Condition: This code is set whenever the Transmission Control Module (TCM) is disconnected from battery power (B+) or ground. It will also be set during the DRBIII Quick Battery Disconnect procedure.
Theory of Operation: A battery backed RAM (Random Access Memory) is used to maintain some learned values. When the battery B(+) is disconnected, the memory is lost. When the B(+) is restored, this memory loss is detected by the TCM. The code is set and the learned values are initialized to known constants or previously learned values from EEPROM (Electronic Erasable Programmable Read Only Memory). This results in the reinitialization of some parameters.
Transmission Effects: Loss of trouble code data. Immediate limp-in mode if power is lost while operating the vehicle. Normal operation is resumed if the power is restored during the same key start.
POSSIBLE CAUSES:
- Battery voltage removed from TCM
- TCM disconnected
- Dead Battery
- Low battery voltage during cranking
- Quick Battery Disconnect by DRBIII or MDS2
- Bad TCM ground circuit
Name of Code: P0891(14) - Relay Output Always On
When Monitored: Ignition key is turned from off position to run position and/or ignition key is turned from crank position to run position.
Set Condition: This code is set if the Transmission Control Module (TCM) senses greater than 3 volts at the Trans Relay Output (switched battery) terminal of the TCM prior to the TCM energizing the relay.
Theory of Operation: The transmission control relay is used to supply power to the solenoid pack when the transmission is in normal operating mode. When the relay is off, no power is supplied to the solenoid pack and the transmission is in limp-in mode. The relay output is fed back to the TCM through pins 16 and 17. It is referred to as the Trans Relay Output circuit or switched battery.
Transmission Effects: The MIL will illuminate and the transmission system defaults to Logical limp-in mode. Logical Limp-in mode results in the same modes of operation as Relay Open Limp-in. Since the relay is stuck "on", the TCM cannot open the relay, and the TCM shifts to 2nd gear.
POSSIBLE CAUSES:
- Relay failure (welded contacts)
- Short to battery in 12-volt supply and/or trans mission control relay output circuit(s)
- Short to voltage
- TCM connector problems
- TCM
Name of Code: P0888(15) - Relay Output Always Off
When Monitored: Continuously.
Set Condition: This code is set when less than 3 volts are present at the Trans Relay Output (switched battery) terminals at the Transmission Control Module (TCM) when the TCM is energizing the relay.
Theory of Operation: The transmission control relay is used to supply power to the solenoid pack when the transmission is in normal operating mode. When the relay is off, no power is supplied to the solenoid pack and the transmission is in limp-in mode. The relay output is fed back to the TCM through pins 16 and 17. It is referred to as the Trans Relay Output circuit or a switched battery.
After a controller reset (ignition key turned to the run position or after cranking engine), the controller energizes the relay. Prior to this the TCM verifies that the contacts are open by checking for no voltage at the switched battery terminals. After the relay is energized, the TCM monitors the terminals to verify that the voltage is greater than 3 volts.
Transmission Effects: The MIL illuminates and the transmission system defaults to Relay Open limp-in mode.
POSSIBLE CAUSES:
- Relay failure (intermittent relay function caused by oxidized or contaminated relay contacts)
- Short to ground or open circuit in the transmission control relay circuit(s)
- TCM connector problem
- TCM
Name of Code: P0725(18) - Engine Speed Input Circuit
When Monitored: Whenever the engine is running.
Set Condition: This code is set when the engine speed sensed by the Transmission Control Module (TCM) is less than 390 RPM or greater than 8000 RPM for more than 2.0 seconds.
Theory of Operation: The TCM uses a simulated Crank Sensor signal to calculate engine RPM. This signal is supplied by the PCM and uses a dedicated circuit called the EATX RPM Signal circuit. If the TCM interprets this signal to be out of range when the engine is running (as reported by the PCM over the bus) the code is set.
Transmission Effects: The MIL illuminates and the transmission system defaults to Relay Open limp-in mode.
POSSIBLE CAUSES:
- Open or short in EATX RPM Signal circuit
- TCM and/or PCM connector problems
- TCM
- PCM
Name of Code: P0716(19) - Bus Communication with Engine Module
When Monitored: Continuously with key on.
Set Condition: If no bus messages are received from the Powertrain Control Module (PCM) for 10 seconds.
Theory of Operation: The TCM communicates with the PCM using the bus. It relies on certain information to function properly. The TCM continuously monitors the bus to check for messages broadcast from the PCM.
Transmission Effects: Delayed 3-4 shifts. No EMCC and early 3-4 shifts for a few minutes after engine is started.
POSSIBLE CAUSES:
- Open or shorted CCD bus(+) or CCD bus(-) circuits
- Bus bias problem
- TCM
- PCM
Name of Code: P0890(20) - Switched Battery
When Monitored: Ignition key is turned from off position to run position and/or ignition key is turned from crank position to a run position.
Set Condition: This code is set if the Transmission Control Module (TCM) senses voltage on any of the pressure switch inputs prior to the TCM energizing the relay.
Theory of Operation: The transmission control relay is used to supply power to the solenoid pack when the transmission is in normal operating mode. When the relay is off, no power is supplied to the solenoid pack and the transmission is in limp-in mode. The relay output is fed back to the TCM through pins 16 and 17. It is referred to as the Trans Relay Output circuit or switched battery.
Immediately after a controller reset (ignition key turned to the run position or after cranking engine), the TCM verifies that the relay contacts are open by checking for no voltage at the switched battery terminals. After this is verified, the voltage at the solenoid pack pressure switches is checked. There should be no voltage on the pressure switches at this time. The TCM will then activate the relay.
Transmission Effects: The MIL illuminates and the transmission system defaults to Relay Open limp-in mode.
POSSIBLE CAUSES:
- Short to battery on one or more pressure switch sense circuits
- TCM connector problems
- Defective TCM
Name of Code: P0871(21) - OD Pressure Switch Sense Circuit
When Monitored: Whenever the engine is running.
Set Condition: This code is set if the OD pressure switch is open or closed at the wrong time in a given gear (see chart).
Theory of Operation: The Transmission system uses three pressure switches to monitor the fluid pressure in the L-R, 24, and OD clutch circuits. The pressure switches are continuously monitored for the correct states in each gear as shown below.
Normal Pressure Switch States
Transmission Effects: Normal operation will be experienced if no other fault codes are present. TCM will ignore the code. Limp-in condition will only occur if code P0871(21) is present with a code P0706(28).
POSSIBLE CAUSES:
- If code P0944(35) is present, ignore code P0871(21) and perform code P0944 diagnostic procedures
- OD pressure switch sense circuit open or shorted to ground between TCM and solenoid pack
- OD pressure switch sense circuit shorted to battery
- Solenoid pack defective
- Loose valve body bolts
- Plugged filter - internal transmission or torque converter failure
- TCM
Name of Code: P0846(22) - 2-4 Pressure Switch Sense Circuit
When Monitored: Whenever the engine is running.
Set Condition: This code is set if the 2-4 pressure switch is open or closed at the wrong time in a given gear (see chart).
Theory of Operation: The Transmission system uses three pressure switches to monitor the fluid pressure in the L-R, 24, and OD elements. The pressure switches are continuously monitored for the correct states in each gear as shown below.
Normal Pressure Switch States
Transmission Effects: If the 2-4 pressure switch is identified as closed in P or N, the code will immediately be set and normal operation will be allowed for that given key start. If the problem is identified for 3 successive key starts, the transmission will go into relay open limp-in mode.
If the 2-4 pressure switch is identified as being closed in 1st or 3rd gear and was not identified as being closed in P or N, then 2nd gear or 4th gear will be substituted for 1st or 3rd gear depending on throttle angle and vehicle speed. A short period of time after the gear substitution, the transmission will return to normal operating mode. If the transmission is shifted back into 1st or 3rd gear through normal operation, and the 2-4 pressure switch remains closed, 2nd or 4th gear will be substituted briefly and then resume normal operation. If four gear substitutions occur in a given key start, the transmission will go into relay open limp-in mode. If the 2-4 pressure switch is open (indicating no 2-4 clutch pressure) in 2nd or 4th gear, the TCM sets code P0846(22) and continues with normal operation. The transmission will only go into relay open limp-in mode if a code P0706(28) is also present. If no 2-4 clutch pressure is present a speed ratio code P0732(52) or P0734(54) will be set and cause the limp-in condition.
POSSIBLE CAUSES:
- If code P0944(35) is present, ignore code P0846(22) and perform code P0944 diagnostic procedures
- 2-4 pressure switch sense circuit open or shorted to ground between TCM and solenoid pack
- 2-4 pressure switch sense circuit shorted to battery
- Solenoid pack defective
- Transmission overheated - Excessive regulator valve leakage in valve body causing high line pressure which results in 2-4 solenoid blow-off in 1st or 3rd gear. May require new valve body if it happens only when hot.
- Loose valve body bolts
- Plugged filter - internal transmission or torque converter failure
- TCM
Name of Code: P0841(24) - L-R Pressure Switch Sense Circuit
When Monitored: Whenever the engine is running.
Set Condition: This code is set if the L-R pressure switch is either open or closed at the wrong time in a given gear.
Theory of Operation: The Transmission system uses three pressure switches to monitor the fluid pressure in the L-R, 24, and OD elements. The pressure switches are continuously monitored for the correct states in each gear as shown below.
Normal Pressure Switch States
Transmission Effects: If a set condition is identified, 1st gear and torque converter lock-up (EMCC) will be inhibited. The vehicle will launch in 2nd gear and shift normally through the gears without allowing EMCC. If during the same key start, the set condition is no longer valid, the transmission will return to normal operation (1st and EMCC available). A relay open limp-in will not occur unless code P0841(24) is accompanied by a code P0706(28).
POSSIBLE CAUSES:
- If code P0944(35) is present, ignore code P0841(24) and perform code P0944 diagnostic procedures
- L-R pressure switch sense circuit open or shorted to ground between TCM and solenoid pack
- L-R pressure switch sense circuit shorted to battery
- Solenoid pack
- Valve body - solenoid switch valve stuck in LU position. (May be accompanied by a code 37)
- Loose valve body bolts
- Plugged filter - internal transmission or torque converter failure
- TCM