P2600, P2601, P2602 and P2603: Coolant Pump Control Circuit Codes
P2600, P2601, P2602, and P2603 describe coolant pump control circuit conditions on vehicles that use an electric coolant pump. A P2601 code, a P2600 code, a P2602 code, or P2603 remains a monitored electrical finding, not proof that the pump has failed. Exact meaning, the monitored pump, and the diagnostic path depend on year, make, model, and powertrain. Record freeze-frame data first, then interpret pump command and feedback with vehicle-specific service information.
Confirm the Code Meaning and Which Coolant Pump It Identifies
P2600 through P2603 are coolant pump control circuit codes, yet the printed description on a scan tool is only a starting point. Manufacturer-dependent numbering requires confirmation of the exact definition and diagnostic procedure for the vehicle's year, make, model, and powertrain. Some layouts use more than one electric coolant pump, so the monitored pump and its cooling function must be identified from vehicle-specific service information rather than assumed from the code number alone.
Before clearing anything, record all stored and pending codes and any available freeze-frame data, including engine speed, load, temperature, and whether the pump was being commanded. A control circuit code identifies a detected condition on that circuit; it does not prove which component failed. The pump, a connector, the wiring harness, a power or ground path, or a control module can all produce similar findings until testing isolates the actual path.
P2600: Coolant Pump Control Circuit Open
After the vehicle-specific definition is confirmed, P2600 typically describes an open in the coolant pump control circuit, meaning the module did not see a complete electrical path where it expected one. An open circuit can exist in a connector, a damaged wiring harness, a missing pump power supply or ground, or inside the pump itself. Where that vehicle's pump circuit uses a fuse or relay, those parts belong in the same inspection list, but only for circuits actually designed that way.
None of those possibilities is a confirmed diagnosis from the code alone. A P2600 code is evidence of an interrupted path, not proof the electric coolant pump has failed. Professional circuit testing is required to locate the interruption before recommending pump replacement, because swapping the pump leaves an open wire, a poor ground, or a dead supply untouched. The correct diagram and enabling conditions for that powertrain keep the search on the actual monitored circuit rather than a look-alike pump elsewhere on the engine.
P2601: Coolant Pump Control Range/Performance
A P2601 code means the module detected coolant pump control range/performance outside its expected criteria. Exact monitored values, enable conditions, and what performance includes for that calibration are vehicle-specific and must come from service information. Possible contributors include how the pump actually runs, the electrical supply feeding it, the control signal that commands it, and, where the design provides it, pump command and feedback disagreement. Those remain hypotheses until measurements match the published tests.
Cooling-system conditions may warrant investigation under that vehicle's diagnostic procedure, but P2601 by itself does not establish low coolant, trapped air, or restricted flow. A technician compares operating conditions in freeze-frame data with live pump command and feedback, looking for a range/performance fault that appears only at certain speeds, loads, or temperatures. Mismatch between commanded and reported operation points toward the control path or the pump's response, while matching electrical values with poor cooling still require the hydraulic checks the manufacturer specifies.
P2602 and P2603: Low and High Control Circuit Conditions
Subject to confirmation in the vehicle's service information, P2602 is generally a coolant pump control circuit low condition and P2603 a circuit high condition. Circuit low and circuit high refer to monitored electrical conditions on the control circuit, not coolant level and not engine temperature. A P2602 code can appear when voltage or current on the sensed line is below the calibrated threshold; P2603 can appear when that same monitored quantity is above its threshold. The labels do not, by themselves, name a short, an open, or a failed module.
Wiring faults, poor connections, pump power supply or ground problems, pump electronics, and control-module faults are all possible, and which ones apply depends on how that circuit is built. Measured voltages need manufacturer specifications and circuit context; a high or low code label cannot establish a specific short or a failed module. Pull-up versus pull-down sensing, whether the module drives the pump directly, and whether a relay sits in the path all change what low and high physically mean on the vehicle in the bay.
Symptoms, Safe Observations, and When to Stop Driving
A malfunction indicator, a temperature warning, or reduced-power operation may accompany these codes, yet noticeable symptoms can also be absent if the monitored pump is not the only cooling path or if the fault is intermittent. Urgency depends on the affected pump's function and on current symptoms. Normal temperature at one moment does not establish that continued driving is safe, because an electric coolant pump that fails to run when commanded can allow heat to climb quickly under load or after shutdown when residual cooling is expected.
Stop safely and shut the engine down for overheating warnings, steam, or a significant coolant leak, then arrange assistance. Owner observations should stay limited to dashboard messages and, when the engine is fully cool and the owner's manual permits it, a look at visible leaks or reservoir level. Never open a hot pressurized cooling system. Keep hands away from electric pumps and fans that may activate unexpectedly. Relay bypasses, directly powering the pump, connector probing, and any high-voltage work belong only to trained technicians with the correct equipment.
Professional Testing and Repair Verification
Diagnosis starts with the correct wiring diagram, a review of related codes, and basic power and ground checks on the identified pump circuit, followed by connector and harness inspection for corrosion, backed-out terminals, or chafing. Where a relay is fitted, a technician tests its operation with approved equipment rather than jumping it. Control commands and any available pump feedback are compared under the enabling conditions in the procedure so an open circuit, a range/performance fault, or a circuit low or high condition can be traced to a measured cause.
The pump or the control module should be blamed only after evidence rules out wiring and supply problems, including intermittent connections that appear with heat or movement. Repair confirmation includes the prescribed functional checks, a review of whether P2600, P2601, P2602, or P2603 returns after a complete drive cycle, and confirmation that cooling operation is appropriate under the relevant conditions. Clearing codes without those checks can hide a remaining control-circuit issue until the next heat-soak or heavy-load run.