2010 Cadillac CTS Sedan AWD V6-3.6L Page 1133
Circuit/System Description
The fuel rail fuel pressure sensor detects fuel pressure within the fuel rail. The engine control module (ECM) provides a 5 V reference voltage on
the 5 V reference circuit and ground on the low reference circuit. The ECM receives a varying signal voltage on the signal circuit. The ECM
monitors the voltage on the fuel rail fuel pressure sensor circuits. When the fuel pressure is high, the signal voltage is high. When the fuel pressure
is low, the signal voltage is low.
Conditions for Running the DTC
Condition 1
* The engine speed is greater than 25 RPM for greater than 30 s.
* DTC P0191 runs once an ignition cycle at engine start up when the condition has been met.
Condition 2 and 3
* The engine speed is greater than 25 RPM for greater than 30 s.
* The engine coolant temperature (ECT) at the previous engine shut down was warmer than 72掳C (162掳F).
* The ECT at engine start is colder than 55掳C (131掳F).
* At engine start, if the ECT is warmer than the intake air temperature (IAT), then the IAT must be within 35掳C (63掳F) of the ECT.
* At engine start, if the IAT is warmer than the ECT, then the ECT must be within 10掳C (18掳F) of the IAT.
* The block heater, if equipped, is not active.
* The engine off time since the previous engine shut down is greater than 4.2 h.
* DTC P0191 runs once an ignition cycle at engine start up when the above conditions have been met.
Conditions for Setting the DTC
Condition 1
DTC P0087, P2187, or P2188 is set, and the fuel pressure at ignition ON is less than 120 kPa (17.4 psi) for greater than 4 s or for a cumulative of
30 s.
Condition 2
DTC P0088, P2177, or P2187 is set, and the fuel pressure at ignition ON is greater than 1.5 MPa (218 psi) for greater than 4 s or for a cumulative
of 30 s.
Condition 3
The fuel pressure at ignition ON is greater than 1.5 MPa (218 psi) and a fuel pressure increase of greater than 350 kPa (51 psi) occurs during the
fuel pump prime. The condition exists for greater than 4 s or for a cumulative of 30 s.
Action Taken When the DTC Sets
* DTC P0191 is a Type A DTC.
* A message center or an indicator may display Reduced Engine Power.
Conditions for Clearing the DTC
DTC P0191 is a Type A DTC.
Diagnostic Aids
A condition with the fuel tank fuel pump module or the fuel pump control module may set this DTC.
Reference Information
Schematic Reference
Engine Controls Schematics (LLT) (See: Diagrams/Electrical Diagrams/Powertrain Management/System Diagram)Engine Controls Schematics
(LF1) (See: Diagrams/Electrical Diagrams/Powertrain Management/System Diagram)
Connector End View Reference
Component Connector End Views (See: Diagrams/Connector Views)
Description and Operation
Fuel System Description (See: Powertrain Management/Computers and Control Systems/Description and Operation/Fuel System Description)
