Ten codes which should I start with ? P0506. P0507.p0410. P0106. P0107. P0306. P0335.P0385. So I'm thinking I have bad sensors and more the one vacuum hose crack of disconnect. I just got this car cheap. 2001 dhs. After looking for disconnects and changing oil and spark plugs and wires. Which code should I tackle first? Crankshaft sensor, camshaft sensor? Mad airflow sensor or secondary airflow injection system? I will fix it all just takes time. Thanks.

Start with looking at scan data on a scan tool , not a code reader
If the PCM detects a MAP sensor signal voltage that is excessively low, DTC P0107 will set.
The PCM calculates a predicted value for the MAP sensor based on throttle position and engine speed. The PCM then compares the predicted value to the actual MAP sensor signal. DTC P0106 will set if the MAP sensor signal is not within the predicted range.
This does not mean the sensor is bad ,could be a wiring problem ,computer etc....
P0306 is a misfire on cylinder # 6 This would be a good one to start with , could ruin the CAT .
The powertrain control module (PCM) uses dual crankshaft position (CKP A and CKP B) sensors in order to determine crankshaft position.
If the PCM determines that CKP sensor A is at fault, DTC P0335 will set. The PCM will switch from angle based mode to Time Based mode B using CKP sensor B signal input.
Diagnostic Aids
If the condition is intermittent, refer to Intermittent Conditions in Symptoms.
Ignition system DTCs set with the ignition in the START position if the starter relay or the starter is inoperative. When the PCM enables starter operation, the PCM also initiates the diagnostic test routines for DTCs P0335, P0340, and P0385. The PCM will not receive signal input from the CKP and CMP sensors if a condition exists which prevents the engine from cranking. When this occurs, the DTCs will set.
If DTC P0615 is set, diagnose DTC P0615 first. If DTC P0335, P0340, and/or P0385 are set and no trouble is found, check for the following conditions:
• Is there a no-crank condition or an intermittent no-crank condition?
• Was an attempt made to crank the engine with the shift lever not in P/N?
Procedures for Selecting Crank Position Sensing Decode Mode
Diagnosing the crankshaft position sensors may require enabling a specific decode mode (Angle, Time A, or Time B). To enable a specific crank decode, using the scan tool, perform the following steps:
• Turn the ignition to the RUN/ON position.
• Select Engine Output Controls.
• Select Crank Position Sensing Decode Mode.
• Select the desired mode (Angle, Time A, or Time B) by pressing SELECT STATE.
• Command the decode mode by pressing COMMAND STATE.
The commanded state remains valid for the current ignition cycle. A specific decode mode can not be commanded with the engine running, or after commanding a desired decode mode. To command a different decode mode, you must cycle the ignition OFF and ON.

DTC P0385
The PCM uses two basic methods of decoding the engine position: Angle Based and Time Based (using either CKP A or CKP B sensor input). During normal operation, the PCM uses the angle based method. In order to operate in this mode, the PCM must receive signal pulses from both CKP sensors. The PCM uses the signal pulses to determine an initial crankshaft position, and to generate MEDRES (24X reference) and LORES (4X reference) signals. Once the initial crank position is determined, the PCM continuously monitors both sensors for valid signal inputs. As long as both signal inputs remain, the PCM will continue to use the angle based mode.
When either CKP signal is lost, the PCM will compare the MEDRES signal to the camshaft position (CMP) sensor signal. If the PCM detects a valid CMP signal, and the MEDRES to CMP signal correlation is correct, the PCM determines that CKP sensor A is at fault. However, if the MEDRES to CMP correlation is incorrect, the PCM determines that CKP sensor B is at fault. If the PCM determines that CKP sensor B is at fault, DTC P0385 will set. The PCM will switch from angle based mode to Time Based Mode A using CKP sensor A signal input.

DTC P0410
Circuit Description
The secondary air injection (AIR) pump used on this vehicle lower tail pipe emissions during start-up. The AIR system consists of the following items:
• The AIR pump
• The shut-off valves
• The vacuum control solenoid valve
• The system hoses and piping
• The AIR relay, the fuses, and the related wiring
The powertrain control module (PCM) uses the AIR relay in order to control the AIR pump. The PCM also controls the AIR vacuum control solenoid valve that supplies vacuum to the AIR shut-off valves. With the AIR system inactive, the AIR shut-off valves prevent air flow in either direction. With the AIR system active, the PCM applies ground to the AIR relay, and the vacuum control solenoid valve. Fresh air flows from the pump, through the system hoses, past the shut-off valves, and into the exhaust stream. The air helps the catalyst quickly reach normal working temperature; thus lowering the tail pipe emissions on a start-up. The PCM tests the AIR system for the following conditions:
• AIR System (Overall system including both banks, and results in DTC P0410)
• AIR System Bank 1 (DTC P1415)
• AIR System Bank 2 (DTC P1416)
• AIR Relay (DTC P0418)
• AIR Vacuum Control Solenoid (DTC P0412)
The PCM runs two tests to diagnose the AIR system: Passive, and Active. Both tests involve a response from the fuel control HO2 sensors (HO2S Bank 1 Sensor 1 and HO2S Bank 2 Sensor 2). If both passive tests pass, the PCM takes no further action. If either part of the passive test fails, or is inconclusive, the PCM initiates the Active tests. If the PCM determines that the HO2S voltages did not respond as expected during the tests, the DTC will set. For further information concerning the AIR System and system tests, refer to

DTC P0506 DTC P0507
The idle air control (IAC) valve is located in the throttle body. The IAC valve consists of a movable pintle, driven by a gear attached to an electric motor called a stepper motor. The IAC valve motor is a 2-phase bi-polar permanent magnet stepper motor that is capable of highly accurate rotation, or movement, every time the polarity of a winding is changed. This change in polarity can be seen when observing a test lamp connected between ground or B+ and an IAC valve circuit while the powertrain control module (PCM) is attempting to change engine RPM. The test lamp will flash on or off each time the polarity is changed. The PCM does not use a physical sensor to determine IAC pintle position, but uses a predicted number of counts, one count represents one change in polarity which equals one step of the stepper motor. The PCM counts the steps that have been commanded in order to determine the IAC pintle position. The PCM uses the IAC valve to control engine idle speed by changing the pintle position in the idle air passage of the throttle body. This varies the air flow around the throttle plate when the throttle is closed. In order to determine the desired position of the IAC pintle at idle or during deceleration, the PCM refers to the following inputs:

Important: Ensure that the engine speed stabilizes with each commanded RPM change in order to determine if engine speed stays within 100 RPM of the commanded RPM.
Set the parking brake, and block the drive wheels.
Install a scan tool.
Start the engine.
Turn OFF all the accessories.
With the scan tool RPM control function, slowly increment engine speed to 1,700 RPM, then to 600 RPM, then to 1,800 RPM.
Exit the RPM control function.
Does the engine speed stabilize within 100 RPM of the commanded RPM during the above test?


011 Idle Speed Problems Scan Data For Idle Control

016 Engine Misfire Crank and Cam Signals