To troubleshoot Ford error codes, you must first identify the specific error codes and problems that trigger them. Common error codes with Ford include P0401, P0402, P1100, P1039 and P1135.
A defective exhaust gas recirculation vacuum modulator or a restriction in the exhaust gas circulation passages can trigger the P0401 error code. Replacing the vacuum modulator and ensuring there is no carbon build up in the exhaust gas circulation can help resolve this problem. A faulty mass air flow sensor can cause poor fuel economy and the check engine light turning on for no reason. To fix this problem, replace the mass air flow sensor.
A P0402 error code indicates excessive flow of exhaust gas recirculation. A P1039 error code indicates an improper Ford speed signal, while P1135 indicates failure of the ignition switch. Erratic turn signal operation errors occur when a turn signal flasher relay is faulty. Replacing the flasher can help to resolve this problem. The error can also result from a worn out key or a fault in the start circuit leading to failure of the ignition switch. Replacing the ignition key and repairing the start circuit can resolve this problem.
Error code P0402 is triggered by lack of proper exhaust gas recirculation system feedback to the computer from the manifold absolute pressure sensor or differential pressure feedback sensor. To fix this problem, consult a Ford maintenance expert.