Question about Dodge Caravan
How to retreive the trouble codes stored in the engine control computer
in Dodge, Chrysler and Plymouth vehicles prior to OBD II...
The self diagnosis information contained in the SBEC or SMEC ( computer ) can be accessed either by the ignition key or by using a scan tool, the scan tool needs to be plugged in to the diagnostic connector in the engine compartment to read the codes and parameters on the digital display screen.
We will focus on the alternate method using the ignition switch since most people don't have a scan tool. To obtain the codes using the ignition key method, first set the parking brake and place the vehicle in Park if is automatic or in neutral if it has a manual transaxle.
Raise the engine speed to a[[roximately 2500 RPM's and slowly let the speed down to idle. Cycle the air conditioning system on then off. If the vehicle has an automatic transmission, with your foot on the brake, select each position on the transmission ( reverse, drive, low etc. ) and bring the shifter back to Park. This will allow the computer to obtain any fault codes that might be linked to any of the sensors controlled by the transmission, engine speed or AC system.
To display the codes on the dashboard through the check engine light, turn the ignition key On, Off, On, Off and finally On without starting the vehicle. The codes will begin to flash, the check engine light will blink the number of the first digit then pause and blink the number of the second digit, for example:
For code 23 ( throttle body temperature sensor circuit ) the check engine light will flash twice, there will be a pause followed by 3 flashes.
Take note that certain criteria must be met for a fault code to be entered into the engine controller memory. The criteria can be a specific range of engine RPM, engine temperature or input voltage to the engine controller. It is possible that a fault code for a particular monitored circuit may not be entered into the memory despite the malfunction. This may happen because the fault code criteria hasn't been met, for example:
The engine must be operating between 750 and 2000 RPM in order to monitor the MAP sensor circuit correctly. If the engine speed is raised above 2400 RPM, the MAP sensor output circuit shorts to ground and will not allow a fault code to be entered into the memory.
The opposite can also occur:
A trouble code can be entered into the memory that suggests a malfunction within another component that is not monitored by the computer, for example: A fuel pressure problem cannot register a fault code directly but instead it will cause a rich/lean fuel mixture problem. Causing an oxygen sensor malfunction code stored in the computer. Be aware of the interrelationship of the sensors and circuits and the overall relationship of the emissions control and fuel injection systems.
Clearing the codes:
The codes can be cleared by disconnecting the negative battery cable for at least 15 seconds, on OBD II models the codes can only be cleared with a scan tool.
For turbocharged engines, codes 26 and 27 are related to the injector driver circuits. Code 26 is related to injector driver circuit 1, and indicates that the injector circuit is either open or shorted. The Power Limited light will not be lit and the system will not enter limp mode. For Throttle Body Injector (TBI) — single fuel injector systems, the most common 2.2 and 2.5 engine systems — code 26 is thrown when peak injector current is not reached.
Possible Reasons for Code 26Poor wiring or connection - Read the page ‘How to troubleshoot drivability issues’. Check the wiring and connections from the logic module to injectors #1 and #2 for Turbo engines. Check the harness from the TBI injector to the computer. Clean and re-grease the connectors with dielectric grease.
Injector driver transistor failure (turbo engines) – When the injector driver is working properly the signal the voltage to the injector should jump to 12vdc when injector is on and drop to 0vdc when injector is on. These signals can be measured from the power module (or SMEC). If you don’t see these voltages at the harness where it connects to the injector ‘and’ you have insured that the harness is good from the injector connector to the power module (or SMEC) then the power module should be replaced.
Injector failure (TBI engine) – Check the resistance of the injector. If it is too high or if it is zero ohms (an open circuit), the injector must be replaced.
I suggest read this article about faults/code-26 and NOTES.
Hope this help.
Posted on Apr 29, 2010
Hi! The injector sensors may have been tripping thats why it wont show on first start. RIght after the self diagnosed it would be the time that the injectors fault will show, then it will run rough acting like a fail safe. Thats the reason why it goes good at first and may trip when restarted. The best thing to do is have the injectors checked. Hope this helps and have a good one!
Posted on Apr 25, 2010
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Posted on Jan 02, 2017
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