Hello everyone. The saga of putting my engine theft 19' Z06 rages on. I'm having trouble locating the code for P16A1. Sensor Communication Circuit High Voltage (System 00) Test not passed since DTC cleared, test failed since DTC Clear, History DTC, Test not passed since Power Up. Have already done all the procedural checks that this code calls for, and still the same code. Checked grounds, plugs, all the ECM, TCM, and BCM connections as well. All advice welcome, this car does have a new GM alternator on it and throttle body.

 

Have you measured signal, ground, and reference voltage at the throttle position sensor? Results?

 

Don't know what you mean by "procedural checks" were done but here is the factory flow chart below...if this testing is over your head seek out an auto electrical shop in your area....unfortunately we can't diagnose it for you over the Internet !!!...if all your checks were visual that is not good enough.

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 P0121Throttle Position Sensor 1 Performance
DTC P0122Throttle Position Sensor 1 Circuit Low Voltage
DTC P0123Throttle Position Sensor 1 Circuit High Voltage
DTC P0222Throttle Position Sensor 2 Circuit Low Voltage
DTC P0223Throttle Position Sensor 2 Circuit High Voltage
DTC P16A0Sensor Communication Circuit Low Voltage
DTC P16A1Sensor Communication Circuit High Voltage
DTC P16A2Sensor Communication Circuit Performance
DTC P2135Throttle Position Sensors 1-2 Not Plausible

Diagnostic Fault Information

Circuit Short to Ground Open/High Resistance Short to Voltage Signal Performance 5 V Reference P06A3 P0122*, P0222*, P16A0 P06A3 P0121, P16A2, P2135* Serial Data P0122*, P0222*, P16A0 P0122*, P0222*, P16A0 P0123*, P0223*, P16A0**, P16A1**, P16A2** P0121, P16A2, P2135* Low Reference — P0123*, P0223*, P16A1 — P0121, P16A2, P2135* * This DTC sets when there is an internal component issue: Q38 Throttle Body
** A short to voltage causes P16A1 to set. If DTC P16A0, P16A1, P16A2 set at the same time, an intermittent circuit condition exists.

Typical Scan Tool Data

Throttle Position Sensor 1 Circuit Short to Ground Open Short to Voltage Operating Conditions:

• Engine = Running
• Accessories = Off

Parameter Normal Range: 3.75 to 4.75 V 5 V Reference 5.0 V 5.0 V 5.0 V Serial Data 5.0 V 0.0 V 0.0 V Low Reference — 0.0 V —

Throttle Position Sensor 2 Circuit Short to Ground Open Short to Voltage Operating Conditions:

• Engine = Running
• Accessories = Off

Parameter Normal Range: 0.45 to 0.90 V 5 V Reference 0.0 V 0.0 V 0.0 V Serial Data 0.0 V 5.0 V 5.0 V Low Reference — 5.0 V —

Circuit/System Description

For an overview of the component/system, refer to: Throttle Actuator Control (TAC) System Description
Circuit Description 5 V Reference Regulated voltage supplied by the control module. Serial Data The control module input circuit has an internal resistance connected to 5 V.
Digitally encoded information for communication between devices. Low Reference Grounded through the control module.

Component Description Q38 Throttle Body The assembly has several functions:

• The throttle valve is actuated by a bidirectional DC motor. A spring pulls the valve to a rest or default position, in which the valve is almost closed. The throttle actuator motor can push against the force of the spring to open or close the valve. The more current flow through the motor, the more the valve moves.
• The throttle body contains a contactless inductive position sensor. A fixed transmitter coil excites a movable rotor, which in turn induces a current in a fixed receiver coil. The current varies with the angle of the rotor. Electronics inside the sensor convert the current into digital data which is transmitted via a serial data circuit to the ECM.

K20 Engine Control Module The control module contains a microprocessor used to process input data to control outputs.
The control module controls a series of actuators to ensure optimal engine performance. The control module does this by reading values from a variety of sensors, interprets the data and adjusts the engine actuators accordingly.

Conditions for Running the DTC

P0121

• DTC P0102, P0103, P0107, P0108, P0112−P0114, P0117, P0118, P0335, P0336 = Not set
• Engine Speed = 500 to 6,900 RPM
• Engine Coolant Temperature = −7 to 126°C (19 to 257°F)
• Intake Air Temperature = −20 to 125°C (−4 to 257°F)

Frequency the DTC runs = Continuously After the running conditions are met

P0122, P0123, P0222, P0223, P16A0, P16A1, P16A2, P2135

• { P0122, P0123, P0222, P0223, P16A0, P16A1, P16A2 } DTC P06A3 = Not set
• { P2135 } DTC P0122, P0123, P0222, P0223, P06A3 = Not set
• Ignition = On or Engine = Running
• Ignition Voltage = Greater than 6.4 V

Frequency the DTC runs = Continuously After the running conditions are met

Conditions for Setting the DTC

P0121

Throttle Position Sensor 1 = Stuck in range — For greater than 1 s

P0122

Throttle Position Sensor 1 = Less than 0.3 V — For greater than 1 s

P0123

Throttle Position Sensor 1 = Greater than 4.7 V — For greater than 1 s

P0222

Throttle Position Sensor 2 = Less than 0.3 V — For greater than 1 s

P0223

Throttle Position Sensor 2 = Greater than 4.6 V — For greater than 1 s

P16A0

Serial Data circuit = Less than 0.5 V — For greater than 1 s

P16A1

Serial Data circuit = Greater than 4.1 V — For greater than 1 s

P16A2

Serial Data circuit = Message Counter Incorrect / Too Many Pulses / Too Few Pulses

P2135

Throttle Position Sensor 1, 2 = Not within 7-10% of each other — For greater than 1 s

Actions Taken When the DTC Sets

DTCs listed in the DTC Descriptor Category = Type A DTC — Exceptions listed below
DTC P0121 = Type B DTC

• Reduced Engine Power = Active
• P16 Instrument Cluster = Reduced Engine Power
• Under certain conditions, the control module commands the engine Off.

Conditions for Clearing the DTC

DTCs listed in the DTC Descriptor Category = Type A DTC — Exceptions listed below
DTC P0121 = Type B DTC

Diagnostic Aids

• A high resistance condition on the throttle position and throttle actuator control circuits could cause a DTC to set.
• If the accelerator pedal is pressed all the way down, the throttle blade angle and the scan tool Throttle Position angle parameter will only go to an angle less than 40%.
• Under cold start conditions, it might happen briefly that the desired and the actual throttle blade position do not match.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference
Component Connector End Views

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

Note: If you were sent here from DTC P0068, P0101, P0106, P1101 » Refer to Circuit/System Testing.

1. Ignition » On / Vehicle » In Service Mode
2. Verify DTC P0601-P0606, P06A3, P16F3 is not set.
   • If any of the DTCs are set
     Refer to: Diagnostic Trouble Code (DTC) List - Vehicle
   • If none of the DTCs are set
3. Verify the scan tool parameter: Throttle Body Idle Air Flow Compensation = Less than 90%
   • If 90% or greater
     Refer to: Throttle Body Cleaning
   • If less than 90%
4. Verify DTC P0122, P0123, P0222, P0223, P16A0, P16A1, P16A2, P2135 is not set.
   • If only DTC P0122, P0123, P0222, P0223, P2135 is set
     Replace the component: Q38 Throttle Body
   • If DTC P16A0, P16A1, P016A2 and one or more of the DTCs P0122, P0123, P0222, P0223, P2135 is set
     Refer to: Circuit/System Testing
   • If none of the DTCs are set
5. Perform the scan tool control function: Throttle Sweep » Start
   Verify the scan tool parameter: Throttle Position Sensors 1 and 2 = Agree
   • If not the specified state
     Replace the component: Q38 Throttle Body
   • If the specified state
6. Verify DTC P0122, P0123, P0222, P0223, P16A0, P16A1, P16A2, P2135 is not set.
   • If any of the DTCs are set
     Refer to: Circuit/System Testing
   • If none of the DTCs are set
7. Verify the scan tool parameter: MAP Sensor = The value should be within the range listed in the table: Altitude Versus Barometric Pressure
   • If not in the specified range
     Refer to: DTC P0106, P0107, or P0108
   • If in the specified range
8. Engine » Running
9. Verify the scan tool parameter: MAP Sensor = 22 to 52 kPa (3.2 to 7.5 PSI) — The value should change with accelerator pedal input.
   • If not in the specified range or does not change
     Refer to: DTC P0106, P0107, or P0108
   • If in the specified range and changes
10. Observe the following scan tool parameter: MAF Sensor & Engine Speed.
11. Increase the engine speed slowly to 3,000 RPM and then back to idle.
12. Verify the scan tool parameter: MAF Sensor = The value should change smoothly and gradually as the engine speed is increased and decreased.
    • If the value does not change smoothly and gradually
      Refer to: DTC P0101-P0103
    • If the value changes smoothly and gradually
13. 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 does not set
14. All OK.

Circuit/System Testing

Note:

• Disconnecting the component electrical connector causes additional DTCs to set.
• It may take up to 2 min for all vehicle systems to power down before an accurate ground or low reference circuit continuity test can be performed.

1. Ignition/Vehicle & All vehicle systems » Off
2. Disconnect the electrical connector: Q38 Throttle Body
3. Test for less than 5 Ω between the test points: Low Reference circuit terminal 4 & Ground
   • If 5 Ω or greater
   1. Disconnect the electrical connector: K20 Engine Control Module
   2. Test for less than 2 Ω between the test points: Low Reference circuit terminal 4 @ Component harness & The other end of the circuit @ Control module harness
      • If 2 Ω or greater » Repair the open/high resistance in the circuit.
      • If less than 2 Ω » Replace the component: K20 Engine Control Module
      
      
   • If less than 5 Ω
4. Ignition » On / Vehicle » In Service Mode
5. Test for 4.8 to 5.2 V between the test points: 5 V Reference circuit terminal 5 & Low Reference circuit terminal 4
   • If less than 4.8 V
   1. Ignition/Vehicle » Off
   2. Disconnect the electrical connector: K20 Engine Control Module
   3. Test for infinite resistance between the test points: 5 V Reference circuit terminal 5 @ Component harness & Ground
      • If less than infinite resistance » Repair the short to ground on the circuit.
      • If infinite resistance
   4. Test for less than 2 Ω between the test points: 5 V Reference circuit terminal 5 @ Component harness & The other end of the circuit @ Control module harness
      • If 2 Ω or greater » Repair the open/high resistance in the circuit.
      • If less than 2 Ω » Replace the component: K20 Engine Control Module
      
      
   • If greater than 5.2 V
   1. Ignition/Vehicle » Off
   2. Disconnect the electrical connector: K20 Engine Control Module
   3. Ignition » On / Vehicle » In Service Mode
   4. Test for less than 1 V between the test points: 5 V Reference circuit terminal 5 @ Component harness & Ground
      • If 1 V or greater » Repair the short to voltage on the circuit.
      • If less than 1 V » Replace the component: K20 Engine Control Module
      
      
   • If between 4.8 and 5.2 V
6. Test for 4.8 to 5.2 V between the test points: Serial Data circuit terminal 3 & Ground
   • If less than 4.8 V
   1. Ignition/Vehicle » Off
   2. Disconnect the electrical connector: K20 Engine Control Module
   3. Test for infinite resistance between the test points: Serial Data circuit terminal 3 @ Component harness & Ground
      • If less than infinite resistance » Repair the short to ground on the circuit.
      • If infinite resistance
   4. Test for less than 2 Ω between the test points: Serial Data circuit terminal 3 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: K20 Engine Control Module
      
      
   • If greater than 5.2 V
   1. Ignition/Vehicle » Off
   2. Disconnect the electrical connector: K20 Engine Control Module
   3. Ignition » On / Vehicle » In Service Mode
   4. Test for less than 1 V between the test points: Serial Data circuit terminal 3 @ Component harness & Ground
      • If 1 V or greater » Repair the short to voltage on the circuit.
      • If less than 1 V » Replace the component: K20 Engine Control Module
      
      
   • If between 4.8 and 5.2 V
7. Test or replace the component: Q38 Throttle Body

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair: Diagnostic Repair Verification

• Throttle Body Assembly Replacement
• For control module replacement, programming, and setup refer to: Control Module References

 

Good news. After having a professional electrical diagnostic service stop by and do a deeper dive into this code. It unraveled ABS codes and the need to program all kinds of systems. It is now a happy camper and is heading to the tuner on Monday to complete the upgrades and have the bumper installed. Then off to detail, and then I will present my 7-month ongoing project in all its glory. Thank you for all the helpful insights and technical data. I truly appreciate this forum and the broader Corvette community. Pictures coming soon.