P1070 on 2016-2018 Cadillac ATS: Auto Start/Stop System Fault Causes and Fixes

What's Unique About the 2016-2018 Cadillac ATS

For this generation of the Cadillac ATS and its platform-mate, the Cadillac CTS, the P1070 code is highly specific. General Motors issued a series of Engineering Information bulletins (PIE0497) to investigate this exact code, ultimately pinpointing cut or damaged wiring at the K176 Start/Stop control module in the trunk as a primary cause. This makes diagnosis more direct than for generic faults, pointing technicians toward a known wiring vulnerability or a secondary, but also documented, software issue requiring an ECM update (TSB 17-NA-162). The system uses an ultracapacitor, also called the Voltage Stabilization System, to provide power for restarts, which is different from many other start/stop systems that rely solely on a second battery.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Check Engine Light (Malfunction Indicator Lamp) is on.
• Auto Start/Stop system is inoperative.
🎬 Watch: Why your auto start stop system might not engage.
• A 'Start/Stop System Disabled' message may appear on the Driver Information Center (DIC).

Most Likely Causes

1. Damaged Wiring at K176 Start/Stop Control Module 🔴 High Probability GM's engineering investigations (PIE0497 series) specifically called out checking for cut wiring at the X1 connector of the K176 control module, located in the trunk. This indicates a likely issue with the harness routing, tension, or vulnerability to damage from items in the trunk. The investigation concluded with a known root cause, directing technicians to standard service procedures for the fix.
   How to confirm: Visually inspect the wiring harness and X1 connector at the K176 Start/Stop Control Module, located behind the driver's side trunk liner. Pull back any protective tape or loom and carefully check each wire for cuts, chafing, or breaks. The damage may be subtle.
   Typical fix: Repair the damaged section of the wire harness using appropriate splicing techniques and heat-shrink protection, as outlined in TSB PI1519B.
   Est. part cost: $5-$20
2. Engine Control Module (ECM) Software Anomaly 🟡 Medium Probability → Shop Engine Control Module (ECM) As documented in TSB 17-NA-162, a specific software issue can cause this code to set. This bulletin superseded a previous one (PIC6225) that only advised clearing the code, indicating a persistent software problem was identified.
   How to confirm: A GM dealer or a qualified shop with access to GM's TIS2WEB service can check the current software calibration on the ECM against the latest available version to see if the update for TSB 17-NA-162 is needed.
   Typical fix: Reprogram the Engine Control Module (ECM) with the latest software calibration. This is a software-only fix and requires no parts.
   Est. part cost: $0
3. Poor Ground Connection ⚪ Low Probability TSB PI1519D, which covers a range of Start/Stop system codes including P1070, points to checking the G402 ground nut at the Start/Stop Capacitor for proper torque and for paint under the connection, which would create a poor ground. The capacitor is located in the trunk.
   How to confirm: Locate the Start/Stop Capacitor (also called the Voltage Stabilizer or Multifunction Energy Storage Capacitor) in the trunk. Inspect the G402 ground connection. Ensure the nut is torqued to specification (9 N·m or 80 lb in) and that there is a clean, paint-free metal-to-metal contact. The G402 ground can be accessed from under the vehicle, behind the left rear wheelhouse liner.
   Typical fix: Disconnect the main 12V battery ground first. Then, remove the G402 ground nut, clean any paint or corrosion from the stud and contact surface with a wire brush or sandpaper, and re-torque the nut to specification.
   Est. part cost: $0

Rare But Worth Checking

• Failing Start/Stop Capacitor (Voltage Stabilizer Module): → Shop Voltage Regulator While wiring and software are more common, the capacitor itself (GM Part #23176212 or #23413621) is a core component. A failure in this module can cause various Start/Stop related codes. It should be considered after verifying wiring, software, and grounds are correct.
• Faulty K176 Start/Stop Control Module: It is possible for the control module itself to fail, but this is much less common than wiring or software issues. The part number has been listed as 24287225, later superseded by 24276865. This part should only be replaced after all other diagnostic steps have been exhausted.

Diagnosis Steps

1. Connect an OBD-II scanner and confirm P1070 is the active or stored code. Note if it is 'Current' or 'History'.
2. Check for any available Technical Service Bulletins (TSBs) related to P1070 for your vehicle's VIN. Specifically, check if the ECM software update from TSB 17-NA-162 has been performed.
3. If the software is outdated, have the ECM reprogrammed by a dealer or qualified shop. Clear the code and see if it returns.
4. If the software is current or the code returns, access the trunk and remove the driver's side liner to locate the K176 Start/Stop Control Module.
5. Carefully inspect the wiring harness and the X1 connector going into the module. As per GM engineering bulletins PIE0497A/B, look for any visible signs of damage, such as cuts, chafing, pinched wires, or corrosion. This is the most common failure point.
6. If wiring damage is found, perform a wire-to-wire repair using approved splicing methods and heat-shrink tubing.
7. If no wiring damage is visible, locate the Start/Stop Capacitor (Voltage Stabilizer Module) in the trunk and inspect the G402 ground connection for tightness and cleanliness, as per TSB PI1519D. Ensure it is torqued to 9 N·m (80 lb in).
8. If all wiring and grounds are confirmed to be good, further diagnostics on the Start/Stop Capacitor and the K176 Control Module may be necessary using a multimeter to check for proper voltage and resistance according to factory service information. Before handling the capacitor, use a GM-compatible scan tool to command it to discharge for safety.

Parts You'll Likely Need

• ECM Reprogramming — A known software anomaly is a primary cause for this code, and an update is the specified fix per TSB 17-NA-162.
  OEM price range: $100-$200
  Aftermarket price range: N/A
• Wiring Repair Supplies — Damaged wiring at the K176 control module in the trunk is the most commonly documented physical cause.
  Trusted brands: 3M
  OEM price range: $5-$20
  Aftermarket price range: $5-$20
• Start/Stop Capacitor (Voltage Stabilizer Module) (OEM #23176212, 23413621) — A rare but possible cause of the fault if wiring, grounds, and software are confirmed to be good.
  Trusted brands: ACDelco, GM Genuine Parts
  OEM price range: $150-$250
  Aftermarket price range: $100-$180

Technical Service Bulletins (TSBs) & Recalls

• 17-NA-162: Supersedes PIC6225 and advises reprogramming the ECM for a P1070 fault.
• PIC6225: An early bulletin that advised simply clearing the DTC P1070.
• PIE0497C: Concluded the engineering investigation, indicating a root cause was found and to refer to standard Service Information (SI) for repair.
• PIE0497B / PIE0497A: Engineering bulletins requesting field information to find the root cause of P1070, specifically asking technicians to check for cut wires at the K176 control module's X1 connector.
• PI1519D: Details procedures for checking the G402 ground at the Start/Stop Capacitor for a host of Stop/Start system codes, including P1070.
• PI1519B: Details procedures for wire-to-wire repairs and capacitor safety related to a host of Stop/Start system codes, including P1070.

Platform-Specific Known Issues

• GM issued TSB 17-NA-162 specifically to address DTC P1070 with an ECM software update.
• A series of Engineering Information bulletins (PIE0497A, PIE0497B, PIE0497C) were released to investigate and ultimately identify a root cause for P1070, pointing heavily toward wiring issues at the K176 module in the trunk.
• The wiring harness in the trunk appears to be susceptible to damage, either from routing tension or from contact with cargo. The repair involves accessing the module behind the driver's side trunk liner.

Mechanic-Grade Diagnostic Values

• G402 Ground Nut Torque — expected: 9 N·m (80 lb in). Failure: A loose nut can cause a poor ground connection, leading to intermittent faults.
• AutoStop Inhibit Conditions (via GDS2) — expected: A list of parameters showing 'Inactive' to allow an AutoStop event.. Failure: Any relevant parameter showing 'Active' (e.g., 'Battery State of Charge Low', 'A/C Compressor Request') will prevent the system from working and can help pinpoint the root cause beyond the P1070 fault itself.

Scan Tool Commands That Help

• GDS2 (GM Global Diagnostic System 2): Discharge Start/Stop Capacitor — This command MUST be used before physically handling or replacing the Multifunction Energy Storage Capacitor (ultracapacitor) to prevent electrical shock. The system must be safely discharged before service.
• GDS2 (GM Global Diagnostic System 2): ECM Data Display > Autostart Inhibit Reason / Autostop Disable Reason — When diagnosing general start/stop inoperability. While P1070 points to a specific circuit fault, this data list in the ECM can reveal other underlying conditions (low battery, engine temp, etc.) that prevent the system from engaging, which may be useful if no physical fault is found.
• GDS2 (GM Global Diagnostic System 2): SPS (Service Programming System) — Used to perform the ECM software update specified in TSB 17-NA-162. This function downloads the latest calibration from GM's servers and flashes it to the vehicle's ECM.

Wiring & Ground Locations

• K176 Start/Stop Control Module — Located in the trunk, typically mounted on the driver's side behind the trunk liner.. This is the control module for the system. Its X1 connector and associated wiring harness are the most common point of failure (cut/chafed wires) for the P1070 code, as identified in GM engineering bulletins.
• G402 — A ground connection for the Start/Stop Capacitor. It can be accessed from underneath the vehicle, behind the left side rear wheelhouse liner.. TSB PI1519D identifies a poor connection at this ground (due to looseness or paint on the stud) as a potential cause for a range of start/stop system DTCs, including P1070.
• G400 — Another ground terminal in the rear of the vehicle, also mentioned in TSBs related to start/stop system issues.. TSB PI1518A and PI1519B list checking this ground for a poor connection as a diagnostic step for a range of start/stop codes, including P1070.
• Start/Stop Capacitor (Voltage Stabilizer Module) — Located in the trunk area, associated with the G402 ground.. This is the ultracapacitor that provides power for restarts. While the component itself is a rare failure, its connections (power and ground) are critical for system operation.

OEM Part Supersession History

• 23176212 → 86815665 — Part discontinued and replaced by a new number.
  Heads up: Part number 23413621 is also listed for the same application, suggesting multiple compatible parts or revisions may exist. Always verify the correct part number with a dealer using the vehicle's VIN.
• 24287225 → 24276865 — Part updated or revised by the manufacturer.
  Heads up: This is for the K176 Start/Stop Control Module. The newer part number should be used for replacement.

Model Year Variations Within This Range

• 2016: The 2016 model year was the first to introduce the new Stop/Start technology with the ultracapacitor system on the ATS. Early production models can sometimes have unique issues or software versions that are later resolved in subsequent model years.