P2A33

Code

Generic P — Powertrain

AFCM Power Relay Control Circuit Low

Brand: Generic

Type: P — Powertrain

Views: UK: 24 EN: 29 RU: 23

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Blown fuse or fusible link feeding AFCM power relay or its control circuit
Faulty AFCM power relay (coil open or internally shorted)
Short to ground on the relay control/command wire
Poor or corroded connector or wiring (open, high resistance, or intermittent)
Faulty PCM/ECM driver transistor or internal relay driver
Low battery voltage or weak charging system

Symptoms

Malfunction Indicator Lamp (MIL) or warning light illuminated
AFCM or related module not powering up or intermittent operation
Related systems not functioning (depends on what AFCM controls)
No-crank/no-start or stalling if AFCM power is required for engine management
Erratic accessory operation or battery drain in some cases

What to check

Read freeze frame and live data with a scan tool; confirm P2A33 is current or historic
Visual inspection: relay, harness, connectors, fuses, and grounds for damage or corrosion
Check battery voltage and charging system health (should be ~12.6 V resting, 13.5–14.8 V running)
Verify fuse(s) supplying AFCM power and relay coil are intact and correct rating
Verify relay operation by listening/feeling when commanded or by bench-testing the relay
Backprobe relay control and supply pins to measure voltage with relay commanded on and off

Signal parameters

Battery supply to relay power terminal: ~12.0–14.5 V (engine off and running respectively)
Relay coil control signal low threshold: typically
Relay coil control signal high/active: near battery voltage (or switched/pulsed by PCM) when commanded
Typical relay coil resistance: ~50–200 Ω (varies by relay — compare to OE spec)
Expected coil current when energized: roughly 0.06–0.25 A for standard automotive relays (verify with OEM spec)

Diagnostic algorithm

Safety first: park on level ground, key off, apply parking brake. Disconnect diagnostic equipment per shop procedures.
Retrieve and record freeze frame and related codes. Note when the code is set (key on, running, cranking).
Visual inspection: check relay, socket, harness, connectors, fuses, and ground points for corrosion, damage, or looseness.
Verify battery and charging system: record resting voltage and charging voltage with engine running.
Check fuse(s): verify continuity and correct rating for fuse(s) supplying AFCM power and relay coil.
Operate relay: with a scan tool or by commanded activation, listen for relay click. If no click, energize relay coil on bench with 12 V to confirm operation.
Backprobe relay socket: measure supply voltage to power terminal and control/command voltage from PCM with key ON and while commanding relay. Confirm control voltage changes as expected.
If control circuit reads low (
If control wire shows open/high resistance to PCM, repair open or poor connection between relay and PCM.
If wiring and relay check good, test PCM output driver by monitoring with oscilloscope or substitute known-good PCM if available (only after wiring and relay verified).
After repairs, clear codes and perform required drive/operation cycle to verify the code does not return.

Likely causes

Bad or stuck AFCM power relay
Short to ground in relay control circuit between PCM and relay
Open/poor power supply (blown fuse, loose battery/ground)
Corroded or damaged connector at relay or AFCM
Faulty PCM output driver (less likely after wiring/relay checks)

Fault status

⚠️ Status

Stored when the power relay control circuit for the AFCM is detected at an abnormally low voltage by the vehicle control module. May set MIL and store freeze frame data. Typically indicates a wiring, relay, fuse, or driver fault rather than the AFCM itself.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours