P1912

Kickdown Hold Relay Open or Short Circuit to Ground

Powertrain Transmission Control Kickdown Relay Circuit 🟡 Moderate — Fix within a week ⚠️ Drive with Care
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What This Actually Means

In plain language — no jargon

The kickdown relay, which helps the transmission downshift for acceleration, is either stuck open or has a short circuit to ground. It's like a light switch that's either permanently off or electrically broken.

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Symptoms You May Notice

3 known symptoms for this code
Transmission won't downshift when accelerating hard
No engine braking when coasting or slowing down
Check engine light illuminated
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How Your ECU Detects This

Technical sensor logic and voltage thresholds

The ECU monitors the kickdown relay circuit voltage and current draw during acceleration requests. It expects normal relay coil voltage when downshift is commanded and detects a fault when the circuit shows open resistance or excessive ground leakage.

Voltage & Parameter Thresholds

ParameterNormal RangeFault Condition
Relay coil resistance 70-120 ohms Open circuit (∞ ohms) or short to ground (<10 ohms)
Circuit voltage when commanded 11-14V 0V (open) or continuous ground (short)
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Diagnostic & DIY Fix Guide

Check these in order — from cheapest to most complex
1
Kickdown relay
Locate the relay in the engine bay fuse/relay box, remove it, and install a new OEM relay.
2
Relay socket and wiring harness
Inspect the relay socket and connector pins for corrosion or bent terminals; clean or replace the socket if damaged.
3
Ground wire and circuit connections
Check and reseat all ground connections related to the transmission control circuit for loose or corroded terminals.
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When to See a Professional Mechanic

Not all fault codes are safe to DIY

Code P1912 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.

Safety note: OBD-II codes identify the system or circuit where a fault was detected — they do not always identify the exact failed component. A professional mechanic using live sensor data will diagnose the root cause more accurately than replacing parts based on the code alone.
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How to Clear Code P1912

What happens after you fix the fault

Once the fault is repaired, P1912 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.

The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.

✅ Safe to Clear When
  • Fault has been diagnosed and repaired
  • You want to confirm the repair worked
  • Code appeared after a sensor was cleaned
⚠️ Do Not Clear When
  • Preparing for an emissions/PUC test
  • Root cause is still undiagnosed
  • Check engine light is flashing
Emissions test note: Clearing codes resets OBD readiness monitors. Most vehicles need 50–100 km of mixed driving before monitors complete. Do not clear codes immediately before an emissions or PUC inspection.