What it means
Indicates an electrical fault in the RF (#1) hydraulic solenoid circuit (open/short/out-of-range current). Seen widely across GM and generic references. AA1 Car+1
Why it sets
The EBCM commands the RF #1 valve and expects current feedback within a calibrated band. Lack of current, excessive draw, or feedback inconsistency sets the code. AA1 Car
Symptoms
- ABS lamp; possible Service StabiliTrak/ESC message.
- Degraded or asymmetric ABS modulation on the RF channel during events. AA1 Car
Common causes
- Open/short in RF #1 coil or harness; connector corrosion at HCU.
- Internal solenoid coil failure in the HCU.
- Less common: EBCM driver fault. AA1 Car
Diagnostics
- Command test with scan tool; listen/feel for valve click; note status PIDs/current where available.
- Measure coil resistance at HCU vs spec; wiggle harness while watching reading for intermittents.
- Voltage drop test on feed/ground under command to expose high-resistance connections.
- If wiring/coil pass but function is absent or current is wrong, follow SI to evaluate EBCM. AA1 Car
Fixes
- Repair harness/terminals; reseal connectors.
- Replace HCU/EBCM when internal coil/driver failure is confirmed.
- Clear and road-test to verify normal commanded modulation. AA1 Car
Sources: Consolidated DTC lists mapping C0070 = RF solenoid #1; practitioner case references. AA1 Car+1