Encountering a check engine light in your Volkswagen can be unsettling, signaling potential engine trouble. Recently, while leaving my in-law’s, my Jetta illuminated this dreaded light. After a few days of cautious driving, I managed to get my hands on a VAGCOM tool (thanks to a helpful friend!) to diagnose the issue and retrieve the fault codes. The scan revealed two distinct codes:
17058 - Cylinder 4 Glow Plug Circuit (Q13): Electrical Fault
P0674 - 35 - 20 - - - Intermittent
17911 - Load Signal From Alternator Term. DF: Implausible Signal
P1503 - 35 - 10 - - - Intermittent
The glow plug fault (17058) was somewhat familiar, thanks to resources like Wingnut’s Glow Plugs 101 guide, providing a starting point for investigation. However, the second code, 17911, regarding the alternator load signal, left me puzzled. A thorough search within the TDIclub forums, while revealing some information courtesy of Whitedog referencing a Seat site, indicated a general lack of readily available solutions for this specific Vw Code.
Recognizing the gap in readily accessible information, I decided to document my experience and the fix for the VW code 17911. It’s important to note that, unlike the glow plug fault which triggered the check engine light, code 17911, in my case, did not initially illuminate the CEL but was consistently stored in the system. This persistent storage became apparent after clearing the codes each night, only to have the 17911 code reappear after my daily commute. This pattern repeated for three consecutive days, solidifying the presence of a recurring issue indicated by this VW code.
Pinpointing the Problem: The Short Harness and Connector Issue
The root cause of the 17911 VW code lies in a seemingly minor, yet critical, design flaw: a slightly undersized wiring harness. Located at the front of the engine, this harness connects the alternator, voltage regulator, and, if equipped, the A/C compressor to the main wiring harness situated beneath the battery box. Volkswagen’s decision to make this harness approximately 1 inch shorter than necessary creates stress at a crucial four-pin connector (or two-pin connector in models without A/C) positioned near the starter.
This harness contains five essential wires, each playing a vital role in the vehicle’s electrical system:
- Large Red Power Wire: This heavy-gauge wire carries power from the alternator to the fuse panel located on top of the battery.
- Green and Black Wire (A/C Clutch): Dedicated to the A/C compressor clutch, this wire passes through the third pin of the four-pin connector.
- Brown and Black Wire (A/C Clutch): Another wire for the A/C compressor clutch, routed through the fourth pin of the connector.
- Very Small Brown and Red Wire (Voltage Regulator): This thin wire originates from the voltage regulator and travels through the first pin of the connector towards the Engine Control Module (ECM).
- Very Small Blue Wire (Voltage Regulator): Similar to the brown and red wire, this thin blue wire from the voltage regulator also passes through the connector (second pin) on its way to the ECM, the generator indicator light on the dashboard, and the warning chime system.
Upon inspecting my vehicle’s harness, I discovered that wire #4 (the small brown and red wire) was completely severed. Wires #5 and #3 also exhibited significant damage, with cracked sheathing and frayed wires, indicating impending failure. This physical damage to the wiring within the harness was the direct cause of the 17911 VW code and likely contributed to the glow plug code 17058 due to general electrical system disruptions.
DIY Repair: A Step-by-Step Guide to Fixing the VW Code 17911 Harness Issue
To address this VW code 17911 issue, I opted for a hands-on repair approach. The first step involved removing the harness from the car to assess the damage and determine the best course of action. This required removing the battery, battery box, air cleaner assembly, and engine cover to gain sufficient access to the harness’s attachment points.
Once the harness was removed, the extent of the damage became clearer. All wire damage was concentrated within a quarter-inch of the connector, making traditional soldering a potentially challenging task due to the limited wire length. I considered two repair strategies:
- Connector Disassembly and Wire Lengthening: Carefully disassemble the connector, lengthen each damaged wire segment, and then rebuild the connector.
- Connector Removal and Permanent Wiring: Completely remove the problematic connector, lengthen the wires, and create permanent, direct wire connections.
Due to the difficulty in disassembling the connector (it appeared to be non-serviceable) and my assessment that the connector itself was not essential for functionality in this specific application, I chose the second option – connector removal and direct wiring.
Here’s a step-by-step guide to replicate this DIY fix for VW code 17911:
- Preparation and Disassembly: Disconnect the battery and remove the components mentioned earlier (battery, battery box, air cleaner, engine cover) to access the harness.
- Harness Removal: Carefully detach the harness from its various connection points. Note the routing of the harness for reinstallation.
- Connector Removal: Cut the wires on both sides of the four-pin connector, effectively removing it from the harness.
- Wire Stripping and Lengthening: Strip the insulation from the ends of the wires on both the harness side and the component side (alternator, voltage regulator, A/C compressor). Using 16-gauge automotive wire (or similar gauge matching the original wires), cut appropriately sized wire extensions for each of the five wires. Strip the insulation from both ends of these extension wires.
- Soldering and Heat Shrinking: Solder the extension wires to the corresponding wires on both the harness side and the component side. Ensure strong, clean solder joints. After soldering each connection, slide heat shrink tubing over the joint and shrink it with a heat gun or lighter to insulate and protect the connection.
- Wire Loom Protection: Wrap the repaired section of the harness with wire loom or electrical tape to provide additional protection to the new wire segments and maintain a neat harness bundle.
- Reinstallation: Reinstall the repaired harness, carefully routing it as it was originally. Reconnect all harness attachment points. Reinstall the air cleaner assembly, battery box, and battery.
- Testing and Code Clearing: Reconnect the battery and start the vehicle. Monitor for any warning lights. Use a VAGCOM or OBD-II scanner to clear the stored fault codes, including VW code 17911 and 17058.
- Verification: Drive the vehicle and then rescan for fault codes to confirm that the 17911 VW code (and any other related codes) has not returned.
