Introduction to the Case
A 2016 Hyundai Solaris equipped with a 1.4-liter engine and automatic transmission arrived for diagnostics. The owner contacted me with concerns about an illuminated Check Engine light following recent engine rebuild work. According to the owner, the engine seemed to run without any obvious issues, but the warning light was causing concern and required professional investigation.
2016 Hyundai Solaris 1.4 AT with active Check Engine indicator after major engine overhaul
G4FA 1.4-liter engine after complete overhaul with new piston assembly installed
During the initial interview with the owner, important background details emerged. It turned out that a major engine overhaul had recently been performed on the vehicle, which included a complete piston ring replacement. This information immediately suggested certain possibilities for the root cause, but I decided to follow a methodical approach: conduct a comprehensive computer diagnostic scan first, then draw conclusions based on solid data.
Connecting the Diagnostic Equipment
For the vehicle inspection, I used an ELM327 adapter paired with the MotorData OBD mobile application. Since I had previously purchased the advanced diagnostic plugin for this make, all that remained was to establish a connection with the vehicle through the standard OBD-II port and begin the system scan.
During the initial connection to the vehicle’s onboard electronics, the first thing that caught my attention was low voltage at the battery terminals. The battery had likely discharged during vehicle downtime, which is a fairly common situation. After successfully establishing the connection, the diagnostic software identified four electronic control units: engine, automatic transmission, anti-lock braking system (ABS), and supplemental restraint system (SRS). No other electronic equipment was present in this base trim configuration.
The built-in comprehensive scanning function proved particularly useful—it allows you to retrieve trouble codes from all available controllers with a single tap, followed by automatic analysis of the collected data.
Comprehensive System Scan Results
The comprehensive scan results were quite impressive: the engine control unit registered 11 fault codes, while the anti-lock braking system controller showed one additional error. In total, there were 12 faults requiring detailed analysis.
Understanding Diagnostic Code Status Types
Before diving into specific error analysis, it’s important to understand the classification of diagnostic code statuses that the electronic control unit records:
A code marked as “Active” indicates a confirmed fault currently present in the system and continuously monitored by the control module.
A code with “Stored” status points to a fault that was previously recorded in active status, but at the time of diagnostics, the conditions for its detection are no longer met, and the controller has moved it to archived state.
The “Pending” status is assigned to a code during initial registration of fault conditions, when the control module requires a repeat verification to definitively confirm the error.
The algorithm for changing diagnostic code statuses is determined by the specific controller’s software programming. In reality, there are significantly more different statuses, but those listed above are the most common in diagnostic practice.
Detailed Breakdown of Engine Faults
The analysis began with the engine control unit. All detected codes were logically divided into four categories based on the nature of the faults.
Detailed technical information for each code, including possible causes and diagnostic trigger conditions, can be found in the professional version of MotorData Auto Electrician software.
First Category: Valve Timing System Issues
The first group includes two codes—P0011 and P0340, related to camshaft position and its sensor. These errors can indicate problems with the variable valve timing (VVT) actuator or camshaft position sensor.
Second Category: Combustion Process Irregularities
The second group includes codes P0300, P0303, and P0304, which signal ignition misfires. The first code indicates multiple random misfires, while the next two point to problems specifically in cylinders three and four.
Third Category: Sensor Circuit Failures
The third and most numerous group combines five codes: P0117, P0122, P0222, P0616, and P0106. Most of them indicate low voltage levels in the electrical circuits of various sensors, which suggests problems with sensor power supply rather than the sensing elements themselves.
Fourth Category: Charging System Malfunction
The fourth group is represented by code P0626, relating to alternator operation and the battery charging system.
Braking System Error
The anti-lock braking system controller displayed code C1208, which also required attention.
Testing Engine Performance Under Real Conditions
The initial start attempt failed due to the discharged battery. After charging the battery, the engine started without issues. At idle, the engine ran smoothly and steadily with no visible signs of malfunction.
Analytical Methodology and Root Cause Investigation
Here’s the logical reasoning sequence when analyzing the obtained diagnostic data:
Analysis of the first code group raised suspicions regarding possible timing chain stretch or installation errors during the rebuild process, but drawing hasty conclusions would have been premature.
Analysis of the second group with misfire codes suggested either poor fuel quality or ignition system faults. Localized misfires in cylinders three and four could also indicate fuel delivery problems. I decided to temporarily set this group aside as secondary.
The third error group clearly pointed to insufficient voltage in sensor electrical circuits. This allowed me to hypothesize that the problem lay not in the sensing elements themselves, but in their power supply—this version seemed most promising.
If detailed analysis of power supply circuits had been necessary, I could have used the professional MotorData Auto Electrician software with its wire tracing feature. This mode allows quick navigation between different modules: from the schematic, you can instantly jump to the control unit connector pinout, identify ground point locations, find the position of the needed relay or controller, and view technical parameters for sensor testing.
The fourth group unambiguously indicated charging system and alternator failures, which correlated with the low voltage detected during connection.
Identifying the Key Fault
Logic suggested that fixing the charging system problem might lead to automatic disappearance of most other errors if they were consequences rather than causes.
Of course, the possibility of multiple independent faults couldn’t be ruled out, but proper diagnostic methodology requires a systematic approach with elimination of secondary factors and focus on the primary problem.
Based on logical analysis of the entire fault pattern, it became clear that the key code was P0620, relating to the alternator control circuit. Moreover, subsequent checks confirmed that the root of the problem indeed lay in the charging system. And considering that the alternator was removed during the engine overhaul, there was a reasonable assumption about improper connector reconnection or poor contact in the connections.
Practical Fault Elimination
The first step was clearing all recorded error codes from the control unit memory, but they were first saved in the MotorData OBD application for subsequent comparison with possible new codes after reset.
Real-Time Parameter Monitoring and Test Drive
After entering the engine control unit, I launched the live data display mode. The parameters showed that alternator load exceeded 90 percent, while voltage in the vehicle’s electrical system remained critically low. All other engine performance indicators were within normal range and raised no questions.
The engine was warmed up to operating temperature of 80 degrees Celsius, after which a test drive was conducted with various operating modes: aggressive acceleration and braking. This type of driving simulates diverse loads on all vehicle systems and provokes hidden faults to surface.
After the test drive, a repeat system scan was performed. The results were encouraging: only a single code P0620 remained in the control unit memory, which confirmed the correctness of the initial analysis.
All alternator connectors were disconnected and reconnected with careful verification of secure latching. After this, the owner was sent for additional test driving for final verification.
Follow-up Diagnostics After 24 Hours
A follow-up meeting with the owner took place after 24 hours of active vehicle operation. A control scan using the diagnostic scanner and memory check of all control units showed complete absence of any fault codes. The problem was completely resolved!
Conclusions From This Practical Case
This case clearly demonstrates that multiple diagnostic codes were caused by the alternator, or more precisely—unreliable contact in its electrical connectors. Using the MotorData OBD mobile diagnostic application combined with MotorData Professional software allowed rapid fault localization and elimination.
The total time spent on two diagnostic sessions and one test drive amounted to just 30 minutes of actual working time.
This case once again confirms an old truth known to professional auto electricians: electronics is the science of connections. An electrical connection must be present where it’s required by design, and completely absent where it shouldn’t exist.
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