DTC P18A2-P18A4

Automatic Transmission - 10L80 MHS MQC | Diagnostic Information and Procedures | Document ID: 5337122 Diagnostic Instructions Perform the Diagnostic System Check prior to using this diagnostic procedure: Diagnostic System Check - Vehicle Review the description of Strategy Based Diagnosis: Strategy Based Diagnosis An overview of each diagnostic category can be found here: Diagnostic Procedure Instructions DTC Descriptor DTC P18A2 Transmission Park Valve Lock Control Circuit Low DTC P18A3 Transmission Park Valve Lock Control Circuit DTC P18A4 Transmission Park Valve Lock Control Circuit High Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performanc
Control — Terminal 11	P2670	P2671	P2671	—
Control — Terminal 12	P18A2	P18A3	P18A4	—

Circuit/System Description

Circuit	Description
Control — Terminal 11	The output circuit is switched to 12 V to enable the component(s).
Control — Terminal 12	The output circuit is switched to ground to activate the component.

	Component	Description
	K71 Transmission Control Module	The control module contains a microprocessor used to process input data to control outputs. The control module receives information from a variety of sensors, switches and serial data information from other control modules. This information is used to control a combination of solenoid valves to obtain the correct line pressure, gear ratio and torque converter clutch operation.
	M123 Transmission Park Valve Lock Solenoid Actuator	A linear solenoid actuator is an electro-mechanical device that converts electrical power into a
	© 2023 General	Mmoetocrhsa. n iAclal lr piguhsthsi nregs oer vpeudll.ing force or motion.

When the component is commanded on, the park servo valve is held in the out of park position, preventing the transmission from going into park. Conditions for Running the DTC Battery Voltage = Greater than 9 V Ignition and Start Signal = 9 to 32 V Ignition and Start Switch Signal = On Frequency the DTC runs = Continuously — After the running conditions are met — For greater than 1 s Conditions for Setting the DTC P18A2 Control Circuit = Short to Ground — For greater than 1 s P18A3 Control Circuit = Open — For greater than 1 s P18A4 Control Circuit = Short to Voltage — For greater than 1 s Actions Taken When the DTC Sets DTC P18A2, P18A3 = Type A DTC DTC P18A4 = Type B DTC Autostart/Autostop = Disabled Default shift pattern = Enabled Grade braking = Disabled High Side Driver 1 = Disabled Manual Shift Control = Disabled Neutral Idle Mode = Disabled TCC Control = Disabled Transmission Adaptive Pressure Control = Freeze current adapt values Conditions for Clearing the DTC DTC P18A2, P18A3 = Type A DTC DTC P18A4 = Type B DTC Reference Information Schematic Reference Automatic Transmission Controls Schematics Connector End View Reference Master Electrical Component List Electrical Information Reference Circuit Testing Connector Repairs Testing for Intermittent Conditions and Poor Connections Wiring Repairs DTC Type Reference Powertrain Diagnostic Trouble Code (DTC) Type Definitions Scan Tool Reference Control Module References Circuit/System Verification

1. Ignition » On / Vehicle » In Service Mode
2. Verify DTC P2670, P2671 is not set. ⇒ If DTC P2670, P2671 is set Refer to: Diagnostic Trouble Code (DTC) List - Vehicle ⇓ If DTC P2670, P2671 is not set
3. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data. Verify the DTC does not set. ⇒ If the DTC sets Refer to: Circuit/System Testing ⇓ If the DTC is not set
4. All OK. Circuit/System Testing
5. Ignition/Vehicle » Off

Note

When the following connector is disconnected, the ignition cannot be turned off due to lack of a valid park input to the TCM. If the ignition needs to be turned off, the connector will need to be reconnected.

2. Disconnect the electrical connector: X1 @ T12 Automatic Transmission
3. Test for 15 to 25 Ω between the test points: Control circuit terminal 11 (component side) & Control circuit terminal 12 (component side) ⇒ If not between 15 and 25 Ω 3.1. Remove the component: Automatic Transmission Fluid Pan 3.2. Disconnect the electrical connector: M123 Transmission Park Valve Lock Solenoid Actuator 3.3. Test for 15 to 25 Ω between the test points: Control terminal 1 & Control terminal 2 ⇒ If not between 15 and 25 Ω » Replace the component: M123 Transmission Park Valve Lock Solenoid Actuator ⇒ If between 15 and 25 Ω » Replace the component: Automatic Transmission Wiring Harness ⇓ If between 15 and 25 Ω
4. Test for greater than 500 kΩ between the test points: Control circuit terminal 11 (component side) & Transmission Case ⇒ If 500 kΩ or less 4.1. Remove the component: Automatic Transmission Fluid Pan 4.2. Disconnect the electrical connector: M123 Transmission Park Valve Lock Solenoid Actuator 4.3. Test for infinite resistance between the test points: – Control terminal 1 & The component’s housing – Control terminal 2 & The component’s housing ⇒ If less than infinite resistance » Replace the component: M123 Transmission Park Valve Lock Solenoid Actuator ⇒ If infinite resistance » Replace the component: Automatic Transmission Wiring Harness ⇓ If greater than 500 kΩ
5. Ignition » On / Vehicle » In Service Mode
6. Connect a test lamp between the test points: Control circuit terminal 11 @ Component harness (harness side) & Ground
7. Perform the scan tool control function: High Side Driver » On and Off Verify the test lamp turns On and Off. ⇒ If the test lamp does not turn On and Off 7.1. Ignition/Vehicle » Off & Remove » Test Lamp 7.2. Disconnect the electrical connector: K71 Transmission Control Module 7.3. Test for infinite resistance between the test points: Control circuit terminal 11 & Ground ⇒ If less than infinite resistance » Repair the short to ground on the circuit. ⇓ If infinite resistance 7.4. Test for less than 2 Ω between the test points: Control circuit terminal 11 & The other end of the circuit ⇒ If 2 Ω or greater » Repair the open/high resistance in the circuit. ⇒ If less than 2 Ω » Replace the component: K71 Transmission Control Module ⇒ If the test lamp is always On 7.1. Ignition/Vehicle » Off & Remove » Test Lamp 7.2. Disconnect the electrical connector: K71 Transmission Control Module 7.3. Ignition » On / Vehicle » In Service Mode 7.4. Test for less than 1 V between the test points: Control circuit terminal 11 & Ground ⇒ If 1 V or greater » Repair the short to voltage on the circuit. ⇒ If less than 1 V » Replace the component: K71 Transmission Control Module ⇓ If the test lamp turns On and Off
8. Disconnect the electrical connector: K71 Transmission Control Module
9. Ignition » On / Vehicle » In Service Mode
10. Test for less than 1 V between the test points: Control circuit terminal 12 @ X1 (harness side) & Ground ⇒ If greater than 1 V Repair the short to voltage on the circuit. ⇓ If less than 1 V
11. Ignition/Vehicle » Off
12. Test for infinite resistance between the test points: Control circuit terminal 12 @ X1 (harness side) & Ground ⇒ If less than infinite resistance Repair the short to ground on the circuit. ⇓ If infinite resistance
13. Test for less than 5 Ω between the test points: Control circuit terminal 12 @ X1 (harness side) & The other end of the circuit ⇒ If greater than 5 Ω Repair the open/high resistance in the circuit. ⇓ If less than 5 Ω
14. Test or replace the component: K71 Transmission Control Module Component Testing
15. Ignition/Vehicle » Off
16. Remove the component: Automatic Transmission Fluid Pan
17. Disconnect the electrical connector: M123 Transmission Park Valve Lock Solenoid Actuator
18. Test for 15 to 25 Ω between the test points: Control terminal 1 & Control terminal 2 ⇒ If not between 15 and 25 Ω Replace the component: M123 Transmission Park Valve Lock Solenoid Actuator ⇓ If between 15 and 25 Ω
19. Test for infinite resistance between the test points: Each terminal of the component & The component’s housing ⇒ If less than infinite resistance Replace the component: M123 Transmission Park Valve Lock Solenoid Actuator ⇓ If infinite resistance
20. All OK. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair: Diagnostic Repair Verification Control Valve Assembly and Transmission Wiring Harness Installation — M123 Transmission Park Valve Lock Solenoid Actuator For control module replacement, programming, and setup refer to: Control Module References