P2979 – Charge Air Cooler Temperature Sensor Circuit High

System: Powertrain | Standard: ISO/SAE Controlled | Fault type: Circuit High

Definition source: SAE J2012/J2012DA (industry standard)

P2979 indicates the control module has detected a Charge Air Cooler Temperature Sensor Circuit High condition. In plain terms, the sensor signal is being interpreted as higher than expected for the circuit’s operating range, which is typically caused by an electrical issue such as an open in the signal/return path, a short to a voltage source, or a reference/ground problem. Because charge air cooler layouts, sensor types, and monitoring logic vary by vehicle, the same code can set under different operating conditions and may affect performance to different degrees. Always confirm the exact sensor location, pinout, and test specifications using the appropriate service information before testing or replacing parts.

What Does P2979 Mean?

P2979 means the powertrain control system has identified a high input fault in the charge air cooler temperature sensor circuit. The “circuit high” portion describes an electrical signal condition (high voltage/high calculated input), not a confirmed mechanical problem. Under SAE J2012-style definitions, this type of DTC is set when the module sees the sensor circuit behaving as if it is driven high (for example, pulled up by a reference voltage or shorted to power) or when the circuit is effectively open in a way that makes the input read high. Diagnosis should focus on verifying the electrical integrity of the sensor, wiring, connectors, and module inputs.

Quick Reference

• Subsystem: Charge air cooler temperature sensor circuit (charge air cooling/induction temperature sensing path).
• Common triggers: Signal circuit short-to-power, open/poor ground or sensor return, unplugged sensor, connector corrosion/spread terminals, harness damage near heat/vibration areas.
• Likely root-cause buckets: Wiring/connector faults, sensor internal fault, reference/ground integrity issue, module input concern (less common).
• Severity: Usually moderate; may cause reduced power or altered boost/airflow strategy depending on vehicle logic.
• First checks: Verify connector seating, inspect harness routing, check for damaged pins, confirm shared sensor reference/ground health, review freeze-frame data.
• Common mistakes: Replacing the sensor without checking for an open return/ground, ignoring connector pin-fit issues, or overlooking a short-to-power in the harness.

Theory of Operation

The charge air cooler temperature sensor reports charge-air temperature to the control module so it can manage airflow, boost control, and protection strategies. Many designs use a temperature-dependent resistor sensor supplied by a reference and a sensor return, with the module reading a changing voltage signal that corresponds to temperature. Other implementations vary by vehicle, but the core concept is the same: the module expects the signal to move within a plausible electrical window and respond smoothly to operating changes.

A P2979 “circuit high” sets when the module detects the input is higher than allowed for the circuit, often consistent with a short to a voltage source or an open circuit that causes the input to be pulled high internally. The module may substitute a default temperature value, limit boost, or adjust fueling/airflow calculations until the signal returns to a valid range.

Symptoms

• Check engine light: MIL illuminated with P2979 stored as current or pending.
• Reduced power: Limp-mode or torque limiting depending on the control strategy.
• Poor acceleration: Sluggish response, especially under load where charge-air control is active.
• Boost control changes: Underboost/overprotect behavior due to substituted temperature values.
• Rough drivability: Hesitation or uneven power delivery in some operating ranges.
• Inconsistent symptoms: Condition may come and go with vibration or moisture if a connection is marginal.
• Secondary codes: Additional sensor reference/ground or related air-path sensor codes if circuits share supplies.

Common Causes

• Open circuit in the charge air cooler temperature sensor signal wire (broken conductor, backed-out terminal, poor crimp)
• Short-to-power on the sensor signal circuit (chafed harness contacting a voltage feed)
• Sensor ground circuit open or high resistance (missing ground path drives the signal “high” relative to module reference)
• Connector issues at the sensor or module (corrosion, moisture intrusion, poor pin tension, terminal push-out)
• Reference supply circuit fault (reference line shorted to a higher-voltage feed or shared circuit issue, varies by vehicle)
• Charge air cooler temperature sensor internally failed in a way that biases the output high
• Wiring damage near heat/vibration points (routing near charge air plumbing, brackets, or sharp edges; varies by vehicle)
• Control module input/circuit fault (less common; verify all powers/grounds and circuit integrity first)

Diagnosis Steps

Tools that help: a scan tool capable of reading live data and freeze-frame, a digital multimeter, and back-probing leads or approved probe adapters. Access to the vehicle’s wiring diagram/service information is important for identifying the correct sensor pins, reference/ground routing, and connector views. If available, use a breakout lead to avoid damaging terminals during testing.

1. Confirm the DTC and record freeze-frame data. Note any companion codes related to reference supply, sensor grounds, or air path sensors; address power/ground/reference-related codes first if present.
2. Check scan tool live data for the charge air cooler temperature sensor reading and observe whether it is implausibly high or fixed. Compare its behavior to other temperature-related inputs only as a sanity check (do not use this to “prove” failure); focus on confirming a “high input” electrical condition.
3. Perform a thorough visual inspection of the sensor, connector, and harness routing. Look for chafing, crushed sections, contact with hot components, water intrusion, and signs of prior repairs. Repair obvious harness damage before deeper testing.
4. Key off, disconnect the sensor connector, and inspect terminals closely for corrosion, spread pins, push-out, or contamination. Correct terminal fitment issues and ensure the connector locks fully.
5. With the sensor still disconnected, check the signal circuit for a short-to-power. Using the wiring diagram, identify the signal pin at the harness side and test for unwanted voltage present on the signal line with the key on; if voltage is present where it should not be, isolate the harness for a short-to-power or a cross-short to a reference/feed circuit (varies by vehicle).
6. Check circuit continuity (key off, battery negative disconnected if required by service info). Measure continuity end-to-end for the signal wire between the sensor connector and the control module connector. Also test for shorts between the signal wire and nearby power feeds. Any open or short found must be repaired and reverified.
7. Verify the sensor ground circuit integrity. Perform a voltage-drop test on the ground path (under the conditions specified by service information) to confirm the ground can carry current without excessive drop; a poor ground can drive the sensor signal “high” at the module.
8. Verify the sensor reference supply circuit (if the design uses a reference feed). Confirm the reference line is present and stable as defined by service information, and check for short-to-power on the reference circuit if the reference appears higher than expected. If reference/ground circuits are shared with other sensors, isolate by unplugging related sensors one at a time (varies by vehicle).
9. If wiring, reference, and ground tests pass, evaluate the sensor itself. Reconnect the harness and use live data while gently wiggling the connector and harness (wiggle test). If the reading spikes high with movement, the fault is likely an intermittent connection or broken conductor near the connector.
10. If the fault remains consistent, substitute with a known-good sensor only if service information permits and only after confirming circuit integrity. Clear codes and perform a road test while logging live data to verify the signal no longer flags “high” and the monitor completes.
11. If all circuit tests and sensor substitution checks pass but the DTC returns, verify module powers/grounds with voltage-drop testing and re-check connector pin fit at the module. Only then consider a control module input fault as a last-step diagnosis (programming/configuration varies by vehicle).

Professional tip: When the issue is intermittent, prioritize live-data logging during a wiggle test and during the specific operating conditions captured in freeze-frame. A circuit-high fault that appears only with vibration or heat is commonly caused by a partially broken conductor or poor terminal tension; repairing the connection often resolves repeat comebacks more reliably than replacing the sensor alone.

Possible Fixes & Repair Costs

Repair costs for P2979 can vary widely because the same “circuit high” symptom may be caused by wiring faults, connector issues, a biased sensor signal, or a control-module input problem. Time spent on pinpoint testing and harness access often drives the overall cost.

• Repair or replace damaged wiring in the charge air cooler temperature sensor circuit (open ground, rubbed-through insulation, or short-to-power)
• Clean, reseat, or replace corroded/loose connectors and terminals; correct poor pin fit and apply proper terminal tension where applicable
• Restore missing ground or reference integrity by repairing splices, ground points, or shared circuit faults found during testing
• Replace the charge air cooler temperature sensor only after confirming the signal remains high with verified-good power/ground/reference and wiring
• Repair harness routing/retention to prevent recurrence (heat damage, vibration chafe, water intrusion paths)
• If all external circuits test good, diagnose the control-module input and related circuit conditioning; repair/replace only as directed by service information

Can I Still Drive With P2979?

Usually you can drive short distances with P2979, but it depends on how the vehicle manages charge-air temperature input and what other warnings are present. Expect the possibility of reduced power or altered engine response. Do not continue driving if you have severe drivability issues, stalling, a no-start, or any safety-related warnings (such as reduced steering/braking assist). If performance is noticeably limited, have the circuit diagnosed promptly to avoid further complications.

What Happens If You Ignore P2979?

Ignoring P2979 can lead to ongoing incorrect temperature input, which may cause the control module to use fallback strategies that reduce performance and efficiency. Over time, intermittent wiring faults often worsen, potentially creating additional sensor codes, repeated warning lights, or more frequent drivability complaints that complicate diagnosis and increase repair time.

Related Sensor Charge Codes

Compare nearby sensor charge trouble codes with similar definitions, fault patterns, and diagnostic paths.

• P2981 – Charge Air Cooler Temperature Sensor Circuit Intermittent
• P2978 – Charge Air Cooler Temperature Sensor Circuit Low
• P2977 – Charge Air Cooler Temperature Sensor Circuit
• P2963 – Intake Air Metering Control Valve Position Sensor Circuit High
• P2980 – Charge Air Cooler Temperature Sensor Performance
• P0538 – A/C Evaporator Temperature Sensor Circuit High

Key Takeaways

• P2979 indicates the charge air cooler temperature sensor circuit is reporting a high electrical input, not a confirmed mechanical cooling problem.
• Most root causes fall into wiring/connector faults such as short-to-power, poor terminal contact, or open ground.
• Replace the sensor only after verifying circuit integrity with targeted tests.
• Live data review and harness movement (wiggle testing) help catch intermittent high-signal conditions.
• Prompt repair can prevent worsening harness damage and repeated drivability issues.

Vehicles Commonly Affected by P2979

• Turbocharged or supercharged engines that monitor charge-air temperature downstream of compression
• Vehicles equipped with air-to-air or air-to-liquid charge air coolers
• Applications with the temperature sensor integrated into a charge-air duct or cooler housing (design varies by vehicle)
• Vehicles operated in environments that promote connector corrosion or water intrusion
• Vehicles with prior front-end, intake, or cooling-system service where harness routing may have been disturbed
• High-mileage vehicles with brittle wiring insulation near heat sources
• Vehicles used in severe vibration conditions that can loosen terminals over time
• Applications with shared sensor reference/ground circuits where one fault can affect multiple sensors

FAQ

Does P2979 mean the charge air cooler is overheating?

No. P2979 specifically indicates a circuit high condition for the charge air cooler temperature sensor circuit. That points to an electrical signal being higher than expected (for example, a short-to-power or an open ground), not a confirmed temperature or cooling hardware failure.

What electrical problems most often cause a “circuit high” code for this sensor?

The most common causes are a short-to-power on the signal wire, an open ground (or high resistance in the ground path), poor terminal contact that intermittently opens the return path, or moisture/corrosion that biases the signal high. Exact circuit design varies by vehicle, so confirm with service information.

Should I replace the charge air cooler temperature sensor right away?

Not until basic circuit checks are completed. A circuit-high fault is frequently caused by wiring, connector, or ground/reference issues. Replace the sensor only after verifying the harness and terminals are sound and the sensor signal remains abnormally high under controlled testing.

Can a wiring issue elsewhere cause P2979?

Yes. Some vehicles share sensor grounds or reference circuits across multiple sensors. A fault in a shared splice, ground point, or reference feed can push the sensor signal high and set P2979. Checking for other sensor codes and performing voltage-drop testing on shared circuits can help narrow this down.

Will clearing the code fix the problem?

Clearing the code only resets the stored fault; it does not correct the underlying circuit-high condition. If the electrical issue remains, P2979 will typically return once the monitor runs again. After repairs, clear the code and confirm the fix by verifying stable live data and completing a drive cycle as specified in service information.

If P2979 returns intermittently, prioritize connector inspection, harness routing, and wiggle testing while logging live sensor data to catch the moment the signal spikes high.