Locate the air pump relay and fuse first–both are critical for verifying power supply before diagnosing emissions-related faults. The relay, typically found in the under-hood fuse box, should be tested for continuity using a multimeter; resistance above 100 ohms or no click during actuation indicates failure. The 30-amp fuse, often labeled “AIR PUMP,” must show uninterrupted metal link across its blades–corrosion or a broken filament demands immediate replacement with the factory-specified amperage.
The one-way check valve sits between the pump and exhaust manifold, preventing backflow of exhaust gases into the injection system. Remove the hose and inspect for carbon buildup or ruptures; a failed valve will either remain stuck open or closed. Blow through the valve toward the exhaust side–any resistance or air passage backward confirms failure and requires replacement with OEM part ACDelco 213-3062 to avoid secondary damage to the pump.
Trace the vacuum lines from the solenoid valve to the engine’s intake manifold. A cracked or brittle line, especially near the manifold connection, will cause inconsistent air injection and trigger OBD-II codes P0410 or P0411. Use a hand-held vacuum pump to apply 20 inHg at the solenoid outlet; if vacuum holds, the lines are intact–if not, replace them with silicone-grade tubing, ensuring routing avoids heat sources like exhaust headers.
Test the solenoid valve by backprobing the wiring harness connector while cycling the ignition. Voltage at terminal A (grey wire) should read 12V with the engine off; terminals B and C (black/white and purple wires) should ground through the ECM when the pump activates. No voltage at terminal A suggests a fuse or relay issue, while voltage but no ground at B/C indicates ECM failure or an open circuit in the harness. Use a wiring diagram specific to L85 2.2L ECOTEC for pinout verification.
For the pump itself, unplug the connector and measure coil resistance–readings should fall between 15 and 25 ohms. Values below 10 ohms indicate internal shorts, while open circuits mean the pump has failed. Rotate the impeller by hand; binding or excessive noise requires pump replacement, but ensure debris isn’t lodged in the inlet hose before condemning it. Always clear OBD-II codes after repairs and perform a drive cycle to confirm readiness monitors reset properly.
Electrical Flow for the SL Series Emissions Control Pump
Locate fuse #18 in the under-hood power distribution box; it’s the sole 15 A link feeding the diverter solenoid and impeller motor. If the fuse tests open, replace it with an identical rating–no uprating–before touching the relay.
Trace the purple wire from the fuse to relay terminal 85; terminal 86 connects to chassis ground via a black/yellow stripe conductor. Measure voltage at terminal 30 with the ignition in RUN: 11.8–12.4 V must be present. Absence indicates corrosion at the PCM splice labeled “D12” behind the left kick panel.
| Relay Pin | Wire Color | Expected Voltage (KOEO) | Common Failure Mode |
|---|---|---|---|
| 85 | Purple | 12 V | PCM splice oxidation |
| 86 | Black/Yellow | 0 V | Poor chassis connection |
| 87 | Dark Blue | 0 V (12 V when actuated) | Relay contact pitting |
| 30 | Red | 12 V | Shorted pump winding |
At the pump connector, probe pin A (red wire) to ground; voltage drop above 0.3 V suggests a burnt splice beneath the intake manifold cover–remove the cover to access splice “G15”. Crimp a new butt connector and heat-shrink tubing over any exposed copper.
Pin B (dark blue) must toggle from 0 V to 12 V within two seconds of startup. If steady-state voltage persists, reflash the ECM using techline software version 4.008 or later; earlier flashes omit the cold-start threshold logic. Clear stored P0410 and P0411 codes after reflash.
Inspect the impeller housing for ice buildup if ambient temperatures dip below 5 °C; a failed one-way valve upstream of the muffler causes condensation to freeze and block airflow. Replace the valve with part number 21147-31505; aftermarket substitutes lack the anodized aluminum seat required for long-term sealing.
Finally, verify the solenoid’s resistance across its two terminals–expect 30–60 Ω at 20 °C. Readings outside this range mandate solenoid replacement; do not attempt to clean the internal filter screen, as it is press-fitted and non-serviceable.
Finding the Emission Control Pump and Related Parts Under the Hood
Begin by locating the air pump solenoid near the driver’s side strut tower–it’s mounted on a bracket adjacent to the vacuum reservoir. Follow the pressure hose (1/4″ diameter, ribbed reinforcement) downwards to identify the combined pump and check valve assembly, bolted to the engine block just above the exhaust manifold. The pump’s electrical connector uses a two-pin plug with gray housing; trace its wiring to the powertrain control module fuse box (fuse #14, 20A). Disconnect the negative battery terminal before handling components to avoid accidental relay activation.
Key Component Markers
- One-way flow valve: Bronze-colored, 1.5″ diameter, threaded onto the pump outlet–inspect for soot buildup or cracking.
- Air distribution manifold: Aluminum cast, secured with three 10mm bolts beneath the intake plenum–label vacuum lines before removal.
- Oxygen sensor relay: Black rectangular unit, 2.5″ x 1.75″, mounted on the firewall behind the coolant expansion tank (label: “O2 SENS”).
Verify component condition by applying 12V directly to the pump’s terminals: a functioning unit emits a high-pitched whine within 3 seconds; silence indicates internal failure. Replace the check valve if airflow reversal is detected during engine idle (backpressure test: ≤2 psi).
Step-by-Step Pump Circuit and Vacuum Line Routing for Emission Control System
Locate the auxiliary pump relay near the vehicle’s main fuse box, typically mounted behind the left front wheel well or adjacent to the under-hood relay center. Verify relay pin assignments: pin 30 connects to a 12V constant source, pin 85 grounds through the powertrain control module (PCM), pin 86 receives 12V ignition signal from the PCM, and pin 87 outputs to the pump motor. Use a multimeter to confirm continuity between pin 87 and the pump’s positive terminal before proceeding further.
Trace the pump’s ground wire–usually a black/yellow stripe–to the chassis ground point beneath the driver’s side fender. Clean the contact surface with a wire brush, apply dielectric grease, and secure it with a new M8 bolt at 18 Nm torque. If corrosion is present, replace the wire with 14-gauge copper-stranded wire, ensuring the same routing path along the original harness loom to avoid interference with suspension components.
Vacuum Line Connections
Connect the 3/16-inch nylon vacuum line from the pump’s solenoid outlet to the check valve mounted on the exhaust manifold. Cut the line to exact length–avoid excess slack–to prevent chafing against the exhaust heat shield. Secure the connection with a worm-drive clamp, tightening to 1.5 Nm. Inspect the check valve for cracks; replace if flow direction (indicated by an arrow on the valve body) is unclear or if it fails a manual blow test.
Route the downstream vacuum line from the check valve to the diverter valve near the intake manifold. Use a T-fitting if multiple ports exist, ensuring all joints are sealed with vacuum-safe silicone. Test line integrity by applying 15 inHg with a manual vacuum pump; leaks will cause erratic pump operation. Label each line with heat-resistant tape to simplify future diagnostics–mark the pump side “UPSTREAM” and the diverter side “DOWNSTREAM.”
Verify the diverter valve’s electrical connector matches the pump’s relay wiring: the white/black stripe wire supplies 12V, while the brown stripe grounds through the PCM. Probe the connector with a test light at key-on-engine-off to confirm power delivery. If voltage is absent, inspect the PCM’s splice block under the dashboard for blown fusible links–common failure points include the splice near the steering column and at the bulkhead connector.
Finalize the setup by reconnecting the battery and monitoring pump activation during a cold start. Listen for a 3-5 second operation cycle; premature shutdown suggests a vacuum leak or failed check valve. If the pump runs indefinitely, disable the relay and check for a stuck-open diverter valve–replace the valve if resistance exceeds 50 ohms across its terminals.
Key Failure Zones in the SL-Series Injection System
Start diagnostics with the one-way check valve. This component often clogs with carbon deposits or fails from thermal fatigue. Test it by applying low-pressure compressed gas to the inlet–flow should move freely in one direction only. If bidirectional flow occurs, replace it immediately. Verify gasket seals during reinstallation to prevent vacuum leaks.
Inspect the pump relay for overheating signs. Locate the relay in the under-hood fuse box (position B-12 in most layouts). Swap it temporarily with a known-good relay (e.g., horn relay) to isolate faults. Common failure modes include corroded contacts and melted internal solder joints–both require full replacement.
- Solenoid valves (typically two) corrode due to moisture exposure. Check resistance across terminals (spec: 25-40 ohms). Values outside range indicate internal corrosion or broken windings. Clean connectors with electrical contact cleaner and apply dielectric grease during reassembly.
- Vacuum lines degrade over time. Trace each line from the intake manifold to the pump, squeezing them gently–brittle or cracked sections need replacement. Use silicone tubing rated for high temperatures (minimum 300°F) to prevent future failures.
- Pressure hoses develop pinhole leaks. Submerge suspect sections in soapy water while the system operates–bubbles reveal leaks. Replace damaged segments with reinforced braided hose, securing connections with worm-drive clamps (not zip ties).
Control module grounds cause intermittent faults. Locate the primary ground near the strut tower (typically bolted to chassis). Scrape paint from mounting surfaces and secure connections with star washers to ensure conductivity. Measure voltage drop (should be
Electrical Connection Diagnostics
Disconnect the pump motor connector and measure voltage at the harness side with the ignition on–expect 12V during engine start. No voltage indicates a relay, fuse, or wiring issue. Probe the circuit with a multimeter, focusing on these common failure points:
- Fusible link: Check for continuity (spec: 0 ohms) between the link and battery positive.
- Relay socket: Measure voltage at terminal 87 (12V expected) with relay removed.
- PCM wiring: Back-probe PCM connector C2 (pin 63) for signal voltage (5V reference).
- Sensor feedback: Verify the pressure sensor circuit (typically 0.5-4.5V range).
Thermal protection circuits trigger premature shutdowns. Remove the pump cover and inspect the thermal fuse–blown units require pump replacement. If intact, check the motor windings for resistance (spec: 2-4 ohms at room temperature). Higher readings indicate internal shorting, necessitating complete pump replacement.
Exhaust backpressure sensors fail silently. Connect a scan tool to monitor live data–normal readings range 15-22 inHg at idle. Abrupt drops or erratic values suggest a faulty sensor or restricted catalytic converter. Replace sensors calibrated for OEM specifications to avoid calibration errors.