🚨 Diagnostic Profile
- Vehicle/Equipment Make: CADILLAC
- Technical Description: TP Sensor Circuit Intermittent Low Voltage
This Powertrain code (P-prefix) is monitored by the Engine Control Module (ECM) or Powertrain Control Module (PCM). P1122 indicates that the PCM has detected an intermittent low voltage condition on the Throttle Position (TP) sensor circuit. The TP sensor works in conjunction with the Accelerator Pedal Position (APP) sensor on electronic throttle control systems to inform the PCM of throttle blade position. When the PCM sees a voltage reading drop below the expected calibrated range—even briefly—it sets this code. Common causes include a failing TP sensor, corroded or loose electrical connectors at the throttle body, chafed wiring harness insulation causing a short to ground, or a poor ground connection in the engine bay near the throttle body assembly. Because this is an intermittent fault, it may not be present during every drive cycle, and the vehicle may enter a reduced power (engine limp-mode) state when the fault is active, along with illumination of the Check Engine Light.
🚨 Repair Difficulty Tier
- Difficulty Rating: Intermediate
This repair requires a digital multimeter to check voltage drops and continuity across the TP sensor circuit, as well as a capable scan tool to monitor live throttle position data and freeze frame information. While replacing the throttle body assembly is straightforward for a DIYer with moderate mechanical skill, accurately diagnosing an intermittent wiring issue versus a failed sensor requires patience and proper electrical testing procedures, making this a good fit for an experienced DIY enthusiast or a professional technician.
🛠️ Resolution Steps
- Step 1: Preliminary Inspection
Begin by visually inspecting the electronic throttle body connector and wiring harness for signs of corrosion, melted plastic, loose pins, or chafed insulation. Check that the connector is fully seated and locked. Inspect nearby grounds and ensure the harness is not rubbing against any engine components that could cause an intermittent short. - Step 2: Diagnostic Verification
Using a scan tool, access live data and monitor the TP sensor voltage while wiggling the harness and connector near the throttle body to try to replicate the intermittent low voltage condition. With the key on and engine off, backprobe the TP sensor signal wire with a digital multimeter and compare the reading to manufacturer specifications (typically starting around 0.5–1.0V at closed throttle). Check for voltage drops, open circuits, or poor grounds using a multimeter in continuity and voltage drop test modes. - Step 3: Resolution & Reset Process
If wiring or connector damage is found, repair or replace the affected harness section and connector terminals. If the sensor itself is faulty or no longer calibrates correctly, replace the electronic throttle body assembly, as the TP sensor is typically integrated and not separately serviceable. After repair, clear the diagnostic trouble codes with a scan tool, perform a throttle body relearn procedure if required by the vehicle platform, and complete several drive cycles to confirm the code does not return.
📦 Parts, Labor, and Budget Estimates
- Required Components/Software: Electronic throttle body assembly (if needed), wiring harness repair kit/connector terminals, digital multimeter, OBD-II scan tool with bi-directional capability
- Average Component Price: $120 – $280 USD
- Estimated Labor Hours: 1.0 – 2.0 hours
- Total Estimated Budget: $220 – $450 USD