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Engine Control System - 3.6L (LY7) - Introduction: Diagnosis Cadillac STS I

Testing & Diagnostics 3 illustrations ~1150 words

Action Taken When the DTC Sets - Type A

The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.

Action Taken When the DTC Sets - Type B

The control module illuminates the MIL on the second consecutive ignition cycle that the diagnostic runs and fails.

Action Taken When the DTC Sets - Type B1

  1. The following applies to misfire DTCs: If the control module detects a low level or an emission level misfire condition during 2 consecutive trips, the control module illuminates the MIL. If the control module detects a high level or catalyst damaging misfire, the control module flashes the MIL at a rate of once per second. If the control module detects a misfire during 2 non-consecutive trips, the stored conditions are compared with the current conditions. The control module illuminates the MIL when the following conditions occur: The engine load is within 10 percent of the previous test that failed. The engine speed is within 375 RPM of the previous test that failed. The engine coolant temperature is in the same range of the previous test that failed.
  2. The following applies to fuel trim DTCs: If the control module detects a fuel trim condition during 2 consecutive trips, the control module illuminates the MIL. If the control module detects a fuel trim condition during 2 non-consecutive trips, the stored conditions are compared with the current conditions. The control module illuminates the MIL when the following conditions occur: The engine load is within 10 percent of the previous test that failed. The engine speed is within 375 RPM of the previous test that failed. The engine coolant temperature is in the same range of the previous test that failed.

Conditions for Clearing the MIL/DTC - Type A or Type B

  1. The control module turns OFF the MIL after 3 or 4 consecutive ignition cycles depending on the DTC, when the diagnostic runs and does not fail.
  2. An active DTC clears when the diagnostic runs and passes.
  3. Use a scan tool in order to clear the MIL and the DTC.

Action Taken When the DTC Sets - Type C

  1. The control module stores the DTC information into memory when the diagnostic runs and fails.
  2. The MIL will not illuminate.
  3. The driver information center, if equipped, may display a message.

Conditions for Clearing the DTC - Type C

  1. A last test failed, or active DTC, clears when the diagnostic runs and passes.
  2. Use a scan tool in order to clear the DTC.

Diagnostic Trouble Code (DTC) Type(s)

DTCUnited States, Canada, and MexicoUnleaded Export - RPO NA3, NT4, NT7Unleaded Export - RPO NF9
P0008BBC
P0009BBC
P0010BBB
P0011BBB
P0013BBB
P0014BBB
P0016BBC
P0017BBC
P0018BBC
P0019BBC
P0020BBB
P0021BBB
P0023BBB
P0024BBB
P0030BBB
P0031BBB
P0032BBB
P0036BBB
P0037BBB
P0038BBB
P0050BBB
P0051BBB
P0052BBB
P0053BBC
P0056BBB
P0057BBB
P0058BBB
P0059BBC
P0101BBC
P0102BBB
P0103BBB
P0112BBB
P0113BBB
P0117BBB
P0118BBB
P0121BBB
P0122BBB
P0123BBB
P0125BBC
P0128BCC
P0130BBB
P0131BBB
P0132BBB
P0133BBC
P0135BBC
P0137BBB
P0138BBB
P0140BBB
P0141BBC
P0150BBB
P0151BBB
P0152BBB
P0153BBC
P0155BBC
P0157BBB
P0158BBB
P0160BBB
P0161BBC
P0201BBB
P0202BBB
P0203BBB
P0204BBB
P0205BBB
P0206BBB
P0221BBB
P0222BBB
P0223BBB
P0261BBB
P0262BBB
P0264BBB
P0265BBB
P0267BBB
P0268BBB
P0270BBB
P0271BBB
P0273BBB
P0274BBB
P0276BBB
P0277BBB
P0300B1B1C
P0301B1B1C
P0302B1B1C
P0303B1B1C
P0304B1B1C
P0305B1B1C
P0306B1B1C
P0318CCC
P0324BBB
P0327BBC
P0328BBC
P0332BBC
P0333BBC
P0335AAA
P0336AAA
P0338AAA
P0341BBB
P0342BBB
P0343BBB
P0346BBB
P0347BBB
P0348BBB
P0351BBB
P0352BBB
P0353BBB
P0354BBB
P0355BBB
P0356BBB
P0366BBB
P0367BBB
P0368BBB
P0391BBB
P0392BBB
P0393BBB
P0420BBC
P0430BBC
P0442AXX
P0443BBB
P0446BBC
P0449BBB
P0451BBC
P0452BBB
P0453BBB
P0455BBC
P0458BBB
P0459BBB
P0461CCC
P0462CCC
P0463CCC
P0480BBB
P0481BBB
P0496BBC
P0498BBB
P0499BBB
P0506BCC
P0507BCC
P0521CCC
P0522CCC
P0523CCC
P0532CCC
P0533CCC
P0560CCC
P0562CCC
P0563CCC
P0564CCC
P0571CCC
P0581CCC
P0601AAA
P0602AAA
P0604AAA
P0606AAA
P0608CCC
P0615CCC
P0616CCC
P0617CCC
P0625CCC
P0626CCC
P0627BBB
P0628BBB
P0629BBB
P0638AAA
P0645CCC
P0646CCC
P0647CCC
P0650B - No MILB - No MILB - No MIL
P0654CCC
P0691BBB
P0692BBB
P0693BBB
P0694BBB
P0700AAA
P0721BBC
P0722BBC
P0850CCC
P0856CCC
P0864CCC
P1011CCC
P1012CCC
P1013CCC
P1014CCC
P1258AAA
P1551AAA
P1629CCC
P1630CCC
P1631CCC
P1668CCC
P167ABBB
P167BBBB
P1689CCC
P1845CCC
P2008CCC
P2009CCC
P2010CCC
P2066CCC
P2067CCC
P2068CCC
P2088BBB
P2089BBB
P2090BBB
P2091BBB
P2092BBB
P2093BBB
P2094BBB
P2095BBB
P2096BBC
P2097BBC
P2098BBC
P2099BBC
P2100AAA
P2101AAA
P2105AAA
P2107CCC
P2119AAA
P2122AAA
P2123AAA
P2127AAA
P2128AAA
P2138AAA
P2176AAA
P2177B1B1C
P2178B1B1C
P2179B1B1C
P2180B1B1C
P2187B1B1C
P2188B1B1C
P2189B1B1C
P2190B1B1C
P2195BBC
P2196BBC
P2197BBC
P2198BBC
P2227BBC
P2228BBB
P2229BBB
P2231BBC
P2232BBB
P2234BBC
P2235BBB
P2237BBC
P2240BBC
P2243BBC
P2247BBC
P2251BBC
P2254BBC
P2270BBC
P2271BBC
P2272BBC
P2273BBC
P2297BBC
P2298BBC
P2300BBB
P2301BBB
P2303BBB
P2304BBB
P2306BBB
P2307BBB
P2309BBB
P2310BBB
P2312BBB
P2313BBB
P2315BBB
P2316BBB
P2626BBC
P2629BBC
P2636CCC
U0001AAA
U0101AAA
U0121CCC
U0155CCC
U0415CCC
U0423CCC

Diagnostic Trouble Code (DTC) Type(s)

Scheme 27

Scheme 27: Emission Hose Routing Diagram
CalloutComponent Name
1Positive Crankcase Ventilation (PCV) Hose to Cam Cover
2Upper Intake Manifold
3PCV Hose to Intake Manifold
4Throttle Body Assembly
5Evaporative Emissions (EVAP) Canister Purge Solenoid
6Emissions Hose to EVAP Canister

Scheme 28

Scheme 28: Evaporative Emissions (EVAP) Hose Routing Diagram
CalloutComponent Name
1EVAP Service Port Connection
2Fuel Filler Pipe Vapor Recirculation Hose
3Fuel Tank Pressure (FTP) Sensor
4EVAP Purge Canister
5EVAP Vent Valve
6Fill Limit Vent Valve (FLVV)
7Fuel Tank Vent/Rollover Valve
8EVAP Purge Solenoid

Scheme 29

Scheme 29: Fuel Hose/Pipes Routing Diagram
CalloutComponent Name
1Secondary Fuel Sender Assembly - Left
2Primary Fuel Sender Assembly - Right
3Fuel Feed Hose
4Fuel Feed Pipe
5Fuel Pressure Test Connection
6Fuel Rail and Injectors
7Fuel Filter
8Fuel Return Hose
9Fuel Filler Tube
10Fill Limit Vent Valve (FLVV)
11Fuel Tank

Conditions for Running the Idle Learn Procedure

  1. DTCs P0121, P0122, P0123, P0221, P0222, P0223, P0638, P2100, P2101, P2105, P2107, and P2119 are not set.
  2. The engine speed is less than 40 RPM.
  3. The vehicle speed is 0 km/h (0 mph).
  4. The accelerator pedal position is less than 14.9 percent.
  5. The ignition 1 voltage is more than 10 volts.
  6. The engine coolant temperature is between 5-85°C (41-185°F).
  7. The intake air temperature is between 5-60°C (41-140°F).

Emissions Diagnosis For State I/M Programs

This OBD II equipped vehicle is designed to diagnose any conditions that could lead to excessive levels of the following emissions

  1. Hydrocarbons (HC)
  2. Carbon monoxide (CO)
  3. Oxides of nitrogen (NOx)
  4. Evaporative emission (EVAP) system losses

Should this vehicles on-board diagnostic system (ECM) detect a condition that could result in excessive emissions, the ECM turns ON the MIL and stores a DTC that is associated with the condition.

Underhood Inspection

IMPORTANTThis inspection is very important and must be done carefully and thoroughly.

Perform a careful underhood inspection when performing any diagnostic procedure or diagnosing the cause of an emission test failure. This can often lead to repairing a condition without further steps. Use the following guidelines when performing an inspection

  1. Inspect all of the vacuum hoses for correct routing, pinches, cuts, or disconnects.
  2. Inspect any hoses that are difficult to see.
  3. Inspect all of the wires in the engine compartment for the following conditions: Burned or chafed spots Pinched wires Contact with sharp edges Contact with hot exhaust manifolds

Large Leak Test

This tests for large leaks and blockages in the EVAP system. The control module will command the EVAP vent valve ON, closed, and command the EVAP purge valve ON, open, with the engine running, allowing engine vacuum into the EVAP system. The control module monitors the fuel tank pressure (FTP) sensor voltage to verify that the system is able to reach a predetermined level of vacuum within a set amount of time. The control module then commands the EVAP purge valve OFF, closed, sealing the system and monitors the vacuum level for decay. If the control module does not detect that the predetermined vacuum level was achieved, or the vacuum decay rate is more than a calibrated level on 2 consecutive tests, DTC P0455 sets.

Small Leak Test

The engine off natural vacuum, (EONV), diagnostic is the small leak detection diagnostic for the EVAP system. The EONV diagnostic monitors the EVAP system pressure or vacuum with the key OFF. The EONV utilizes the temperature changes and the resulting naturally occurring vacuum or pressure in the fuel tank immediately following a drive cycle. When the vehicle is driven, the temperature in the fuel tank rises. When the vehicle is parked with the engine OFF and key OFF, the temperature in the fuel tank will continue to rise for a period of time, and then begin to decrease. The EONV diagnostic relies on this temperature change, and the corresponding pressure change to determine if an EVAP system leak is present. The EONV diagnostic is designed to detect leaks as small as 0.51 mm (0.020 in). The diagnostic can determine if a small leak is present based on vacuum or pressure readings in the EVAP system. When the EVAP system is sealed a finite amount of pressure or vacuum will be observed. When a 0.51 mm (0.020 in) leak is present, little or no pressure or vacuum is observed. If the test reports a failing value, DTC P0442 will set.

Canister Vent Restriction Test

If the EVAP vent system is restricted, fuel vapors will not be properly purged from the EVAP canister. The control module tests this by commanding the EVAP purge valve ON, open; and commanding the EVAP vent valve OFF, open; and monitoring the FTP sensor for an increase in vacuum. If vacuum increases more than a calibrated value, DTC P0446 sets.

Purge Valve Leak Test

If the EVAP purge valve does not seal properly, fuel vapors could enter the engine at an undesired time, causing driveability concerns. The control module tests for this by commanding the EVAP purge valve OFF, closed; and vent valve ON, closed; sealing the system, and monitoring the FTP for an increase in vacuum. If the control module detects that EVAP system vacuum increases above a calibrated value, DTC P0496 sets.