The P2799: Auxiliary Transmission Fluid Pump Control Circuit High code indicates that there is a higher-than-expected voltage present in the control circuit for the auxiliary transmission fluid pump. This issue could be caused by a faulty auxiliary pump, a wiring short to power, or a malfunction in the control module. Proper functioning of the auxiliary transmission fluid pump is crucial for maintaining transmission fluid flow, especially in high-load or stop-start conditions, to ensure efficient cooling and lubrication.
P2799 – Quick Overview
| Code | Information |
|---|---|
| Meaning | P2799: Auxiliary Transmission Fluid Pump Control Circuit High |
| Is it serious? | Yes, high voltage in this circuit can lead to improper pump operation, resulting in poor fluid circulation, overheating, and potential damage to the transmission components. |
| Possible causes | – High voltage in auxiliary transmission fluid pump control circuit – Faulty pump or wiring – Control module issues |
| How to diagnose? | – Measure voltage in the auxiliary transmission fluid pump control circuit – Inspect wiring and connectors – Check for shorts or damage – Replace components as needed |
P2799 Meaning
The P2799: Auxiliary Transmission Fluid Pump Control Circuit High code indicates that the voltage in the auxiliary transmission fluid pump control circuit is above the acceptable range specified by the manufacturer. This may be caused by a short to power in the wiring, a faulty pump, or an issue with the control module (TCM). A high voltage condition can prevent the auxiliary pump from operating correctly, which could lead to transmission fluid overheating or other malfunctions.
Step-by-step diagnostic guide
| Action | Description | Tools Needed |
|---|---|---|
| Check for Other Codes | Use an OBD-II scanner to determine if there are any additional related codes. Other codes may provide further insight into transmission or electrical system issues, especially concerning voltage regulation. | OBD-II Scanner |
| Measure Voltage in the Auxiliary Pump Control Circuit | Use a multimeter to measure the voltage in the auxiliary transmission fluid pump control circuit. Compare this measurement to the manufacturer’s specifications. If the voltage is higher than expected, it suggests a potential issue such as a short to power or a control module malfunction. | Multimeter, Manufacturer Specifications |
| Inspect Wiring and Connectors | Perform a detailed inspection of the wiring and connectors associated with the auxiliary transmission fluid pump. Look for signs of damaged insulation, loose connectors, or corroded terminals. A short to power could result from exposed wiring contacting a power source. Repair or replace any damaged components. | Flashlight, Safety Gloves |
| Check for Shorts to Power | Use a multimeter to check for a short to power in the wiring that connects to the auxiliary transmission fluid pump. A short can cause the circuit to have a higher-than-expected voltage. Follow the wiring harness and look for any unintended contact with a power source, and repair any issues found. | Multimeter |
| Test the Auxiliary Transmission Fluid Pump | Test the pump for proper functionality using a diagnostic tool. Verify that the pump is operating within manufacturer specifications. If the pump is drawing more power than expected, it may be faulty and require replacement. | Diagnostic Tool, Multimeter |
| Inspect Control Module Signals | Use a diagnostic tool to verify if the transmission control module (TCM) is functioning correctly and that it is not providing excessive voltage to the pump. A malfunction in the TCM could send too much power, leading to the high voltage code. If needed, consider reprogramming or replacing the TCM. | Diagnostic Tool, Manufacturer Software |
| Check Relay and Fuse | Inspect the relay and fuse associated with the auxiliary transmission fluid pump circuit. A stuck relay could cause continuous power supply, resulting in a high voltage reading. Ensure the relay and fuse are in good working condition, and replace them if necessary. | Multimeter, Fuse Puller |
| Inspect Grounding | Check the grounding points connected to the auxiliary pump control circuit. Improper grounding can cause electrical instability, contributing to an overvoltage condition. Clean and tighten any loose grounds to ensure the circuit is correctly grounded. | Multimeter, Wire Brush |
| Replace Faulty Components as Needed | Replace any components identified as faulty, including the auxiliary transmission fluid pump, wiring, connectors, relays, or even the control module. Ensure all replacements are of high quality and meet the manufacturer’s specifications for optimal performance. | Replacement Pump, Wiring Repair Kit, Relays |
| Clear the Code and Test Drive | After repairs, use an OBD-II scanner to clear the P2799 code. Conduct a test drive to monitor the performance of the auxiliary transmission fluid pump and verify that the high voltage condition has been resolved. Ensure smooth fluid flow and proper cooling of the transmission. | OBD-II Scanner |
| Recheck for Codes | Perform a final scan after the test drive to confirm that the P2799 code has not returned. If the code persists, further diagnostics may be required to determine ongoing high voltage issues affecting the auxiliary transmission fluid pump circuit. | OBD-II Scanner |
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