Check engine light


In the early years of internal combustion engines, mechanical components were put together to make the engine function. The fueling, air injection and spark event were made to be almost independent of electrical or complex electronic systems for efficient engine operation. As it is obvious that these components ride on each other and change shape, due to increase in temperature as well as tear and wear starts to show on them, these could go unawares until the components starts to make a noise or fail. This ultimately leads to breakdown.



Besides, the response of the systems at times could be delayed, making it difficult for a prompt response of drivers demand while in motion. It could make it difficult for necessary adjustment of exhaust gas emission from the vehicle exhaust system which could have a devastating impact on the environment.


Today’s vehicle still rides a lot on the template of old vehicle systems. However, several changes have taken place in terms of increased electronics as well as presence of monitors to different system on the vehicle.



The infusion of electronics in these vehicles systems has made it easy for an immediate response to drivers demand and as well as a proper adjustment of air fuel mixture to ensure an environmentally friendly vehicle exhaust by-products and for ease diagnosis and repairs.


These electronics however add to the complexity of existing technology and determination of the faults.


It can sometimes not be physically examined unlike when it is the issue of wear and tear of the mechanical system.



With these in mind, the vehicle manufacturers have put a system in place that helps to check electronics system and alerts the driver of a fault, through a malfunction indicator light. In the case of an engine related fault, it is referred to as the check engine light.


What should you do when the check light comes on?


As understood, the “check light” on is an indication of powertrain related fault, and the fault can only be known by running a diagnostic scan on the powertrain.



The light had been on since I bought the car, should I worry?


This is a question I get many times. Even if the vehicle performs optimally that doesn’t mean everything is okay. The check light could be on for a minor to major faults. The minor faults might not give an obvious performance issue, but the issue is that even in the advent of a critical condition on the powertrain, the same light is what would remain on.



It is however best to have the necessary service done on the vehicle to have the check light off.


What happens when it flashes?


A flashing check engine light would mean that a misfire that is capable of damaging the catalyst converter is happening on the engine. This could be as a result of a bad coil, spark plug, fuel pump etc. It is best to have it attended to as fast as possible to avoid damage to the catalyst.



 Does erasing the light takes off the problem?


The engine computer works like a counter whenever it is erased or reset. It starts all over again and if the concern that brought about the light isn’t taken care of, it would show up. The remedy to put the light off is to solve the problem why it came up.


This piece is written by my mentee Ibrahim Ogundele.


Generic codes

P0981: Shift solenoid ‘D’ control circuit range/performance



Meaning


The engine control module commands gear shifts by turning the shift solenoid valves on/off. When there is an open or short circuit in any shift solenoid valve circuit, the ECM detects the problem and illuminates the engine light and stores the diagnostic trouble code and the ECM performs the fail-safe function and turns the other shift solenoids valves in good condition on/off.


Possible causes


Faulty shift solenoid ‘D’

Shift solenoid ‘D’ harness is open or shorted

Shift solenoid ‘D’ circuit poor electrical connection


P0982: Shift solenoid ‘D’ control circuit low


Meaning



When shift solenoid valves A, B, C, D, and E are turned on, the hydraulic pressure circuit opens. The hydraulic pressure circuit supplies/discharges hydraulic pressure to/from each clutch according to the combination of the on/off status of the shift solenoid valves. The powertrain control module commands the driver circuit to turn on the shift solenoid valve. The circuit diagnoses malfunctions such as a circuit short or open, and sends back a return signal during the PCM’s command. When the return signal does not match the PCM command to turn on the shift solenoid valve, the PCM detects a malfunction and stores a diagnostic trouble code.



Possible causes


Faulty shift solenoid Valve ‘D’

Shift solenoid valve ‘D’ harness is open or shorted

Shift solenoid valve ‘D’ circuit poor electrical connection

 P0983: Shift solenoid ‘D’ control circuit high


Meaning


The engine control module commands gear shifts by turning the shift solenoid valves on/off. When there is an open or short circuit in any shift solenoid valve circuit, the ECM detects the problem and illuminates the engine light and stores the diagnostic trouble code, and the ECM performs the fail-safe function and turns the other shift solenoids valves in good condition on/off.



Possible causes


Faulty shift solenoid ‘D’

Shift solenoid ‘D’ harness is open or shorted

Shift solenoid ‘D’ circuit poor electrical connection

P0984: Shift solenoid ‘E’ control circuit range/performance


Meaning


The engine control module commands gear shifts by turning the shift solenoid valves on/off. When there is an open or short circuit in any shift solenoid valve circuit, the ECM detects the problem and illuminates the engine light and stores the diagnostic trouble code, and the ECM performs the fail-safe function and turns the other shift solenoids valves in good condition on/off.



Possible causes


Faulty shift solenoid ‘E’

Shift solenoid ‘E’ harness is open or shorted

Shift solenoid ‘E’ circuit poor electrical connection

P0985: Shift solenoid ‘E’ control circuit low


Meaning


Shifting from 1st to 5th is performed in combination with “on” and ”off” operation of the shift solenoid valves SL1, SL2, SL3, S4 and SR which is controlled by the engine control module. If an open or short circuit occurs in either of the shift solenoid valves, the ECM controls the remaining normal shift solenoid valve to allow the vehicle to be operated smoothly (Fail safe function).



When is the code detected?


Engine control module detects an open or shorted condition on the solenoid circuit


Possible symptoms


Engine light on (or service engine soon warning light)

Shift shock

Possible causes


Faulty pressure control solenoid valve ‘E’

Pressure control solenoid valve ‘E’ harness is open or shorted

Pressure control solenoid valve ‘E’ circuit poor electrical connection

Faulty engine control module

Low transmission fluid level

Dirty transmission fluid

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