P2990 – Reductant Injector “D” Control Circuit/Open

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

Definition source: SAE J2012/J2012DA (industry standard)

DTC P2990 indicates the powertrain control module has detected an electrical problem described as a control circuit open condition for the reductant injector labeled “D.” In practical terms, the module is not seeing the expected electrical continuity or response on that injector’s control circuit, which can happen if the circuit is unplugged, a wire is broken, or a terminal fit issue prevents current flow. Because reductant delivery strategies and injector naming (A/B/C/D) vary by vehicle, always confirm the exact circuit routing, connector views, and test points in the appropriate service information before testing. Treat this code as an electrical circuit integrity fault until proven otherwise with inspection and measurements.

What Does P2990 Mean?

P2990 means the control circuit for reductant injector “D” is detected as a circuit/open condition. Per SAE J2012 DTC structure, this is an electronically monitored fault where the module commands or monitors the injector control circuit and determines the circuit is not electrically intact (for example, no continuity, an unplugged connection, or a break/high resistance that behaves like an open). The code does not, by itself, confirm a mechanical injector problem or fluid quality issue; it specifically points to the injector “D” control circuit being open or not electrically responsive as expected.

Quick Reference

• Subsystem: Reductant injector “D” electrical control circuit (powertrain aftertreatment reductant delivery control).
• Common triggers: Unplugged connector, broken conductor, poor terminal pin fit, damaged harness near heat/vibration points, or an internal open in the injector/driver path.
• Likely root-cause buckets: Wiring/connector faults, injector electrical open, power/ground feed issues (where applicable), module driver/circuit fault (less common).
• Severity: Usually emissions/aftertreatment impact with possible reduced performance strategies; typically not an immediate safety hazard, but drivability can be affected depending on vehicle strategy.
• First checks: Visual inspection of injector “D” connector and harness, confirm connectors fully seated/locked, check for corrosion or spread pins, verify continuity end-to-end per service info.
• Common mistakes: Replacing the injector without verifying the circuit is intact, overlooking a partially seated connector, or ignoring harness damage near clamps, bends, or hot components.

Theory of Operation

The reductant injector is an electrically actuated valve used by the aftertreatment system to meter reductant into the exhaust stream. The control module typically drives the injector using a dedicated control circuit and monitors circuit integrity by observing electrical behavior when the injector is commanded on and off. Depending on design, the injector may receive a feed with the module controlling the other side, or the module may supply and control the circuit in a different arrangement; the verification method varies by vehicle.

For a circuit/open fault, the module detects that the circuit does not conduct as expected. This can be caused by an open in the wiring, a disconnected connector, a terminal issue that prevents contact, or an internal open in the injector’s electrical path. The module sets P2990 when it cannot achieve or observe the expected electrical response on the injector “D” control circuit during its monitor conditions.

Symptoms

• Warning light: Check engine light illuminated with P2990 stored.
• Reduced aftertreatment performance: Emissions control effectiveness may decrease due to incorrect or disabled reductant dosing.
• Limited power strategy: Some vehicles may enter a reduced performance mode tied to aftertreatment faults.
• Stored related codes: Additional aftertreatment or reductant system DTCs may appear depending on how the system reacts.
• Failed readiness/inspection: Emissions monitors may not complete or may fail due to the active fault.
• Intermittent behavior: Symptoms may come and go if the open is due to vibration-sensitive wiring or a loose connector.

Common Causes

• Open circuit in the reductant injector “D” control wire between the injector and the control module (broken conductor, rubbed-through harness)
• Connector not fully seated at reductant injector “D” or at an intermediate junction, causing an open circuit
• Terminal damage or poor pin fit (spread, backed-out, corroded, or overheated terminals) creating a true open or an effective open under vibration
• Open power feed or open ground for the reductant injector circuit (where injector power/ground routing varies by vehicle)
• Internal open in reductant injector “D” (actuator coil or internal connection fault)
• Harness damage from heat exposure near exhaust/aftertreatment components leading to conductor separation
• Water intrusion in connectors causing corrosion and intermittently open contact
• Control module driver/circuit fault (less common; consider only after wiring and injector integrity are proven)

Diagnosis Steps

Tools: a scan tool capable of reading freeze-frame data, DTC status, and running any available output/actuator tests; a digital multimeter; basic back-probing or breakout leads appropriate for the connector type; and wiring diagrams/service information for the exact vehicle. A test light may help on some circuits, and a scope can be useful for driver-command verification where supported.

1. Confirm the code and capture evidence. Verify P2990 is present, record freeze-frame data and any related aftertreatment or reductant-system DTCs, and note whether the code is current, pending, or history. If other electrical supply or module-voltage codes are present, address those first because they can cause multiple “circuit/open” flags.
2. Check scan data for injector command/feedback context. Using live data (vehicle-dependent), look for any parameters that indicate reductant injector command state, system enable conditions, or aftertreatment readiness. The goal is to understand when the monitor runs and whether the fault sets immediately or only during commanded dosing.
3. Perform a visual inspection focused on opens. With the key off, inspect the harness routing to reductant injector “D” and nearby connectors. Look for chafing, melted insulation, pinched sections, strained wiring, and evidence of previous repairs. Pay particular attention to areas near heat sources and where the harness moves relative to brackets.
4. Connector integrity check (unplug and inspect). Disconnect the injector connector and any accessible intermediate connectors in the circuit. Inspect for backed-out terminals, damaged locks, bent pins, corrosion, moisture, and signs of overheating. Reseat connectors and ensure positive engagement. Correct any mechanical issues before electrical testing.
5. Wiggle test with live monitoring. Reconnect connectors and monitor DTC status or relevant live data while gently wiggling the harness and connector bodies. If the status flips, the engine behavior changes, or the DTC rapidly returns, treat it as a location clue for an open/poor contact rather than replacing parts.
6. Check for power/ground availability where applicable. Circuit design varies by vehicle, so use service information to identify which pins should carry power and which are controlled/returned. With the circuit enabled as specified by service info, verify that the injector circuit has the required power feed and ground path. If power or ground is missing, trace that feed/ground for an open, damaged splice, fuse/relay path issue, or connector problem.
7. Continuity test the control circuit for an open. With the key off and the relevant modules disconnected as required by service information, measure continuity of the reductant injector “D” control wire end-to-end. An open reading indicates a break in the conductor, a disconnected junction, or a terminal that is not making contact. If continuity is borderline or changes when flexing the harness, suspect a partial break or poor pin fit.
8. Check for unintended contact that mimics an open condition. While P2990 is a circuit/open fault type, confirm the control wire is not shorted to other circuits in a way that prevents proper current flow or driver detection. Use resistance checks to adjacent wires and to chassis ground per service procedures; repair any harness damage found, then recheck for an open.
9. Voltage-drop test under load (preferred over static readings). If service information provides a way to command the injector (output test) or run conditions that enable dosing, perform voltage-drop testing across connectors, splices, and grounds while the circuit is being commanded. Excessive drop across a connector or ground path can effectively create an “open” to the driver by limiting current, especially with heat/vibration.
10. Test the injector for internal open. With the injector disconnected, measure the injector’s internal resistance and compare it to service information. An out-of-spec or infinite reading supports an internal open. If the injector is within specification, focus back on wiring, terminals, and the driver path.
11. Verify driver command and circuit response (only after wiring/injector checks). If wiring integrity and injector checks pass, use a scan tool actuator test (or other approved procedure) to command operation and verify that the control module is able to drive the circuit and detect current flow. If the module commands the injector but the circuit response is absent with proven-good wiring and injector, module driver diagnosis may be warranted per service information.
12. Clear codes and validate the repair. After repairs, clear DTCs, run the appropriate enable conditions/drive cycle, and confirm P2990 does not return. Recheck for pending codes and confirm the monitor completes where applicable. If the code returns, repeat the wiggle and voltage-drop tests to locate an intermittent open.

Professional tip: Treat “circuit/open” as a current-flow problem first. A connector that looks clean can still be electrically open due to poor terminal tension or a backed-out pin; this often only shows up during a wiggle test or a voltage-drop test under command. Use service information to identify the exact injector “D” pins, then test from pin-to-pin (not insulation-piercing) to avoid creating new faults.

Possible Fixes & Repair Costs

Repair costs for P2990 vary widely because the root cause can range from a simple connector issue to harness repair or injector replacement. Labor time also depends on component access and whether additional wiring faults are found during testing.

• Repair or replace damaged wiring in the reductant injector “D” control circuit (open conductor, chafing, heat damage, pinched section)
• Clean, reseat, or replace affected connectors/terminals (poor pin fit, corrosion, backed-out terminals, broken locks) at the injector and along the harness
• Restore proper power/ground supply to the reductant injector circuit if testing confirms an open feed or open ground path
• Replace the reductant injector “D” only after verifying the injector coil/circuit is open and wiring/connectors test good
• Repair harness routing/retention to prevent repeat opens (secure loom, add abrasion protection where needed)
• If directed by service information and confirmed by diagnosis, perform control-module related repairs (connector pin issues) or approved software updates

Can I Still Drive With P2990?

Driving may be possible, but it is not recommended to ignore the warning because an open control circuit can disable proper reductant injection and may lead to reduced performance or inducement strategies depending on vehicle design. If you experience reduced power, warning messages that limit speed, or any safety-related symptoms (stalling, no-start, or brake/steering warnings), do not drive; have the vehicle inspected and repaired.

What Happens If You Ignore P2990?

If P2990 is ignored, the system may continue to detect the open circuit and disable or limit reductant dosing, which can cause persistent warning lights, reduced power, and possible restrictions on operation based on emissions-system strategy. Ongoing electrical faults can also worsen due to heat, vibration, or corrosion, making harness repair more involved later.

Related Reductant Injector Codes

Compare nearby reductant injector trouble codes with similar definitions, fault patterns, and diagnostic paths.

• P2986 – Reductant Injector “C” Control Circuit/Open
• P2056 – Reductant Injector Circuit/Open Bank 2 Unit 2
• P2053 – Reductant Injector Circuit/Open Bank 1 Unit 2
• P2050 – Reductant Injector Circuit/Open Bank 2 Unit 1
• P2907 – Exhaust Aftertreatment Fuel Injector Circuit/Open
• P2623 – Injector Control Pressure Regulator Circuit/Open

Key Takeaways

• P2990 indicates an electrical circuit/open condition in the reductant injector “D” control circuit, not a confirmed mechanical failure.
• Most successful repairs start with wiring, connector fit, and terminal integrity checks before replacing parts.
• Use test-driven diagnosis: continuity checks, voltage-drop testing, and harness wiggle testing to locate opens.
• Vehicle response varies by platform; inducement or power limitation may occur even if drivability seems normal at first.
• Fix only what testing proves, then confirm the repair with a proper verification drive cycle per service information.

Vehicles Commonly Affected by P2990

• Vehicles equipped with an SCR aftertreatment system using a reductant injector circuit identified as “D”
• Diesel-powered light-duty trucks and SUVs with urea-based reductant dosing
• Medium-duty applications with aftertreatment dosing control integrated into the powertrain control system
• Commercial vehicles where reductant components are exposed to high heat and road splash
• High-mileage vehicles with harness wear near exhaust/aftertreatment routing
• Vehicles operated in corrosive environments where connector fretting or terminal corrosion is common
• Vehicles that have had recent exhaust, aftertreatment, or underbody service where connectors may be left partially seated
• Vehicles with prior wiring repairs or aftermarket routing changes that increase harness strain

FAQ

Does P2990 mean the reductant injector “D” is bad?

No. P2990 means the control circuit for reductant injector “D” is detected as open. An open can be caused by wiring damage, a disconnected connector, poor terminal tension, or an internal open in the injector. Testing is required to identify which is at fault.

Will clearing the code fix P2990?

Clearing the code may turn the light off temporarily, but if the circuit open is still present the code will return when the monitor runs again. Clear codes only after repairs or to confirm whether the fault is currently active versus history.

What’s the most common place to find the open circuit?

Many opens are found at connectors and terminals: partially seated plugs, corrosion, backed-out pins, broken terminal locks, or strained sections of harness near heat sources and sharp edges. The exact location varies by vehicle, so follow service information and verify with testing.

Can low reductant level cause P2990?

No. A low fluid level is not an electrical open in the injector control circuit. P2990 is specific to a circuit/open condition, so diagnosis should focus on wiring, connectors, injector electrical integrity, and the power/ground/control path.

What should be verified after the repair?

Verify the connector is fully seated and secured, the harness is properly routed and supported, and that the circuit no longer shows an open under a wiggle test. Then clear codes and confirm the monitor completes without returning P2990 using a verification drive cycle as outlined in service information.

For best results, document test findings (where the open was located and how it was verified) so the repair can be confirmed and future repeat failures can be prevented.