U1135 — SCP (J1850) Invalid or Missing Data for Ignition Switch / Starter

U1135 — SCP (J1850) Invalid or Missing Data for Ignition Switch / Starter. A fault in the ignition system. Short, gentle driving to a shop is usually possible. Typical causes: moisture or oil in the spark plug wells, damaged coil wiring or connector, worn spark plugs or wrong plug gap.

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Is it safe to drive?

Drive with caution Drive with caution and avoid load. Ignition faults cause misfires that quickly overheat and destroy the catalytic converter; if the Check Engine Light flashes, stop and fix it first.

How to diagnose with an OBD scanner

  1. Read the code and freeze frame Connect an OBD2 scanner, confirm U1135 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
  2. Check for companion codes and TSBs Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many U0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
  3. Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the ignition system for damage, corrosion, chafing or poor contact.
  4. Subsystem check Swap the coil to another cylinder and see if the fault code follows it.
  5. Subsystem check Inspect spark plugs for wear, oil or carbon tracks and check plug gaps.
  6. Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm U1135 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for U1135 (parts and labor, USD, independent shop rates): Repair coil wiring or connector: $80–$250; Replace an ignition coil: $150–$380; Replace spark plugs: $90–$250. Overall, fixing U1135 usually costs between $80 and $380. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

What does OBD2 code U1135 mean?

U1135 — SCP (J1850) Invalid or Missing Data for Ignition Switch / Starter. A fault in the ignition system. Short, gentle driving to a shop is usually possible. Typical causes: moisture or oil in the spark plug wells, damaged coil wiring or connector, worn spark plugs or wrong plug gap.

Will U1135 clear itself?

Sometimes U1135 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.

What are the symptoms of U1135?

Drivers most often notice: loss of power and jerking, Check Engine Light on, hard starting, especially in damp weather, increased fuel consumption.

How much does it cost to fix U1135?

Repair coil wiring or connector — $80–$250; Replace an ignition coil — $150–$380; Replace spark plugs — $90–$250. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

How do I diagnose U1135 myself?

Start with a scan: confirm U1135, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the ignition system, and verify the suspect component against live data before buying parts.

What does U1135 mean?

When U1135 appears on a scan, it means the control module has flagged a problem in the ignition system: SCP (J1850) invalid or missing data for ignition switch / starter. The fault sits in the vehicle network group of the OBD2 standard.

The module monitors this system continuously while driving. When readings fall outside the expected range for a defined number of drive cycles, it stores U1135 and switches on the warning light. Freeze frame data saved with the code shows the exact conditions — rpm, load, temperature, speed — at the moment the fault was detected, which is the best starting point for diagnosis.

What causes U1135?

  • moisture or oil in the spark plug wells
  • damaged coil wiring or connector
  • worn spark plugs or wrong plug gap
  • faulty ignition control circuit in the ECM
  • failed ignition coil or coil pack

Common symptoms of U1135

  • loss of power and jerking
  • Check Engine Light on
  • hard starting, especially in damp weather
  • increased fuel consumption
  • misfires under load or at idle

How to diagnose U1135

  1. Connect an OBD2 scanner, confirm U1135 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
  2. Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many U0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
  3. Visually inspect the wiring harness and connectors related to the ignition system for damage, corrosion, chafing or poor contact.
  4. Swap the coil to another cylinder and see if the fault code follows it.
  5. Inspect spark plugs for wear, oil or carbon tracks and check plug gaps.
  6. Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm U1135 does not return.

How to fix U1135

Start with the cheapest and most common causes before replacing expensive parts:

  • Repair coil wiring or connector — $80–$250
  • Replace an ignition coil — $150–$380
  • Replace spark plugs — $90–$250

How much does it cost to fix U1135?

Repair cost depends on which component actually failed. Typical scenarios for U1135 (parts and labor, USD, independent shop rates):

  • Repair coil wiring or connector: $80–$250
  • Replace an ignition coil: $150–$380
  • Replace spark plugs: $90–$250

Overall, fixing U1135 usually costs between $80 and $380. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Can you drive with U1135?

Drive with caution and avoid load. Ignition faults cause misfires that quickly overheat and destroy the catalytic converter; if the Check Engine Light flashes, stop and fix it first.

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