P1190

What the Code Means

P1190 belongs to the fuel system category and is logged by the DME as a discrepancy in the injection control loop upstream of the catalytic converter on bank 1. The control unit evaluates mixture formation from sensor readings, and if the actual control value falls outside the calculated limits, it sets this fault.

Under normal conditions the control loop continuously trims fuel delivery based on feedback from the heated oxygen sensor upstream of the catalytic converter. The code means the trim has taken on an incorrect value: either from a real deviation in fuel and air delivery, or from distorted data from one of the sensors involved in the calculation.

Symptoms

By engine behavior:

• hesitation and a jump into limp mode while driving;
• engine rattle or knock, usually in second and third gear at around 2,000 rpm;
• the fault shows up near throttle request points: the classic scenario is a sharp lift off the accelerator at 3,000 rpm followed by acceleration around 2,000 rpm, after which limp mode kicks in again.

One important detail: idle is stable, which points to the fault being tied to transient load conditions rather than to base idle mixture formation.

Diagnosis and Repair

Work from the most likely and easiest-to-check items to the least likely. Components involved in forming the injection trim value:

1. Wiring harness and connectors — check for integrity, corrosion, and secure contact.
2. Intake and fuel system — look for vacuum leaks and check fuel pressure.
3. Injectors — check flow rate and spray pattern.
4. Heated oxygen sensor — evaluate the pre-catalyst readings as the primary mixture feedback element.
5. Mass air flow sensor — an incorrect signal skews the base fuel metering.
6. Engine coolant temperature sensor — a low or high reading shifts the calculated trims.
7. Evaporative emissions control valve — extra fuel drawn through the EVAP system affects the trim value.
8. Engine control module — considered only after all peripheral causes are ruled out.

The link between symptoms and transient conditions (lifting and reopening the throttle around 2,000 rpm) narrows the search: prioritize components whose influence changes with load and airflow — that means intake, fuel delivery, and injectors.