Experiencing a “Reduced Engine Power” message in your GM vehicle can be concerning. One potential culprit behind this issue is Diagnostic Trouble Code (DTC) P0697-00. This code indicates a problem with the 5V Reference Voltage #3 circuit, a critical component that powers several sensors essential for your engine’s operation. As an automotive repair expert at keyfobprog.com, I’ll guide you through understanding and troubleshooting this code.
What Does DTC P0697-00 Mean?
DTC P0697-00, specific to General Motors vehicles, signals a malfunction in the 5V Reference Voltage #3 circuit. This circuit is designed to supply a stable 5-volt power source to a group of sensors. In the case of the 2.4L engine mentioned in your shop manual, the code specifically points to sensors like:
- Manifold Absolute Pressure (MAP) Sensor: Measures the pressure within the intake manifold, crucial for determining air density and adjusting fuel delivery.
- Accelerator Pedal Position Sensor 2: Monitors the position of the accelerator pedal, providing input to the Engine Control Module (ECM) for throttle control.
When the ECM detects an issue within this 5V reference circuit, such as an incorrect voltage level, it triggers the P0697-00 code. This can lead to various drivability problems, including the dreaded “Reduced Engine Power” message.
Symptoms Associated with P0697-00
Besides the “Reduced Engine Power” message, you might observe other symptoms when DTC P0697-00 is present:
- Check Engine Light (CEL) illumination: The most common indicator of any DTC.
- Poor engine performance: Hesitation, stalling, or lack of power.
- Rough idling: Unstable engine speed when stationary.
- Potential issues with related systems: Since the affected sensors are part of the engine management system, other related issues might arise.
Diagnosing DTC P0697-00: Step-by-Step
Troubleshooting P0697-00 requires a systematic approach. Here’s a diagnostic procedure based on the information from your shop manual:
Step 1: Initial Setup and Sensor Disconnection
- Turn the Ignition OFF.
- Locate and disconnect the harness connectors for both the MAP sensor and the Accelerator Pedal Position Sensor 2. This isolates the sensors from the circuit for testing.
Step 2: Voltage Testing
- Turn the Ignition ON (but do not start the engine).
- Using a multimeter, test the voltage between one of the pins on the affected 5V reference circuits (on the vehicle harness side, where you disconnected the sensors) and ground.
- You should be looking for a voltage reading between 4.8 and 5.2 volts. This is the expected range for a healthy 5V reference circuit.
Interpreting Voltage Readings:
- Voltage is Less than 4.8V: This indicates a potential short to ground somewhere in the 5V reference circuit. Proceed to Step 3A.
- Voltage is Greater than 5.2V: This suggests a potential short to voltage in the 5V reference circuit. Proceed to Step 3B.
- Voltage is within 4.8-5.2V Range: This indicates the 5V reference circuit itself might be functioning correctly, but the issue could lie with a sensor or the ECM. Proceed to Step 4.
Step 3A: Testing for Short to Ground (Low Voltage)
If you measured low voltage, you need to check for a short to ground on the 5V reference circuit for each affected component individually.
- Inspect the wiring harness leading to the MAP sensor and Accelerator Pedal Position Sensor 2 for any signs of damage, chafing, or melted insulation that could cause a short to ground.
- Using your multimeter in continuity mode, test for continuity between the 5V reference circuit wire and a known good ground point on the vehicle. Continuity indicates a short to ground.
- If you find a short, repair the wiring. If no shorts are found in the wiring, and voltage remains low after checking both sensor circuits, the ECM might be the issue (though less likely at this stage).
Step 3B: Testing for Short to Voltage (High Voltage)
If you measured high voltage, the test is similar, but you’re looking for a short to voltage.
- Inspect the wiring harness as in Step 3A for damage.
- Using your multimeter in voltage mode, test for voltage between the 5V reference circuit wire and a known 12V power source in the vehicle (like the battery positive terminal or a 12V accessory wire). Voltage present indicates a short to voltage.
- Repair any wiring shorts found. If no shorts are found, and voltage remains high, the ECM could be faulty.
Step 4: Component Isolation with Scan Tool (Advanced)
This step utilizes a scan tool that can monitor live data parameters, specifically the “5V Reference Circuit Status.” Note: As your shop manual mentions, basic scanners might not display this parameter; this is often a feature of dealer or high-end professional scan tools.
- Connect your scan tool and navigate to live data or parameter monitoring. Look for a parameter related to “5V Reference Circuit Status” or similar.
- With the ignition ON and sensors disconnected, the status should ideally show “OK” or a normal indication for the 5V reference circuit (assuming the circuit itself tested within range in Step 2).
- Connect each component (MAP sensor and Accelerator Pedal Position Sensor 2) one at a time, and observe the “5V Reference Circuit Status” parameter on your scan tool after each connection.
Interpreting Scan Tool Data:
- Status Remains “OK”: If the status stays normal after connecting each sensor, it suggests that neither sensor is directly causing the fault. The problem might be intermittent, or potentially related to the ECM if all wiring and sensors appear normal.
- Status Changes to “Malfunction” or Error: If the status changes to indicate a malfunction after connecting a specific sensor, this points to that sensor as the likely culprit. In this case, proceed to Step 5.
Step 5: Signal Circuit Testing (Suspect Component)
If Step 4 indicated a specific sensor might be causing the issue, test its signal circuit for a short to voltage. The shop manual note also mentions that a short to voltage on a signal circuit of certain components can also trigger P0697.
- With the suspect sensor connected, backprobe the signal wire of that sensor.
- Using your multimeter in voltage mode, test for voltage between the signal wire and a known good ground.
- Significant voltage on the signal wire when it shouldn’t be there could indicate a short to voltage within the sensor itself or in its signal wiring.
Resolution based on Signal Circuit Test:
- Signal Circuit Shorted to Voltage: Inspect the signal wiring for shorts and repair. If wiring is good, replace the sensor.
- Signal Circuit Tests Normal: If the signal circuit seems okay, but the scan tool indicated a malfunction upon connecting this sensor, replacing the sensor is the recommended next step.
Step 6: ECM Replacement (Last Resort)
If all wiring tests are normal, sensors have been tested or replaced, and the P0697-00 code persists, the ECM is the most likely remaining cause. ECM replacement should be considered as a last resort after thoroughly eliminating other possibilities.
Key Components and Circuit Locations
To aid in your diagnosis, remember the following component locations and circuit details mentioned in the original article:
- MAP Sensor Plug: Looking at the plug with the clip at the top, the 5V #3 Reference Circuit is the left corner pin (GY – Gray wire).
Alt text: Diagram of a GM MAP sensor connector plug showing pin locations. The 5V Reference #3 circuit is located at the left corner pin, indicated by a gray wire (GY).
- Accelerator Pedal Position Sensor Plug: On the Accelerator Pedal Position Sensor 2 plug, the 5V #3 Reference Circuit is the 4th pin from the left (of 6 pins).
Alt text: Diagram of a GM Accelerator Pedal Position Sensor connector plug with six pins. The 5V Reference #3 circuit is located at the 4th pin from the left.
Note: Wire colors can sometimes vary slightly depending on the exact vehicle year and model. Always refer to your specific vehicle’s wiring diagrams for the most accurate information.
Throttle Body and Accelerator Pedal Sensor Relationship
The original post mentions replacing the Throttle Body. It’s important to note that the Throttle Actuator Control (TAC) system, which manages the throttle body, involves several inputs to the ECM, including:
- Accelerator Pedal Position Sensors
- Throttle Body Sensors
- Ignition Voltage
- Cruise Control Switch
While replacing the Throttle Body might address issues related to its sensors, DTC P0697-00 specifically points to the 5V Reference #3 circuit affecting the MAP sensor and Accelerator Pedal Position Sensor 2. Therefore, even with a new Throttle Body, problems with these other sensors or the 5V reference circuit can still trigger “Reduced Engine Power” and the P0697-00 code.
Conclusion
Diagnosing Gm Dtc P0697-00 requires a methodical approach, starting with basic voltage checks and progressing to component isolation and signal circuit testing. By following these steps, you can effectively pinpoint the source of the 5V Reference Voltage #3 circuit issue and restore your GM vehicle’s performance. Remember to always consult your vehicle’s specific service manual for detailed wiring diagrams and component locations. If you’re not comfortable performing these tests, seeking assistance from a qualified automotive technician is always recommended.
