# TCM Turbo vs DiagonalOBDII

The clearest difference is in-app purchases: TCM Turbo at none against DiagonalOBDII's 4. TCM Turbo also leads on iOS requirement (6.0 vs 18.1). DiagonalOBDII's advantage is update cadence (every 2 weeks vs every 4 months). On price, rating, ratings volume and ads there is nothing between them.

Both are free to download. DiagonalOBDII sells 4 in-app purchases, starting at $12.99 per month. TCM Turbo asks for nothing beyond the download.

On the App Store both sit at effectively the same score — 5.0 for TCM Turbo against 5.0 for DiagonalOBDII. Both are backed by a comparable volume of ratings — 1 and 1 respectively.

TCM Turbo ships an update every 4 months, DiagonalOBDII every 2 weeks. The most recent releases landed on November 1, 2026 and November 4, 2026 respectively.

## The numbers

| Metric | TCM Turbo | DiagonalOBDII |
| --- | --- | --- |
| Price | Free | Free |
| Rating | [5.0 (1 ratings)](https://appshunter.io/ios/app/tcm-turbo/id597232996/reviews) | [5.0 (1 ratings)](https://appshunter.io/ios/app/diagonalobdii/id6743419784/reviews) |
| Number of ratings | 1 | 1 |
| Positive reviews | — | 0.0% of reviews |
| In-app purchases | **No** | Yes |
| Ads | No | No |
| Update frequency | Every 4 months | **Every 2 weeks** |
| Monetization | **Free** | Freemium |
| Size | 3 MB | 24 MB |
| Requires iOS | **6.0** | 18.1 |
| Devices | **iPhone, iPod** | iPhone |
| Age rating | 4+ | 4+ |
| Developer | [Skanbit Software Solutions](https://appshunter.io/developer/410088614) | [Kyle Louderback](https://appshunter.io/developer/1400068218) |

## What reviewers say

### TCM Turbo

[App page](https://appshunter.io/ios/app/tcm-turbo/id597232996)

Access a database of cars available for tuning at TCM TURBO Romania. Browse all models and engine types for chip tuning services. Find distributors, current promotions, and contact the TCM Turbo team.

**Highlights:** Car tuning database, Chip tuning information, Distributor map, Current promotions, Portfolio with images, Contact team

**Features:** macOS Compatibility

**In-app purchases:** none


### DiagonalOBDII

[App page](https://appshunter.io/ios/app/diagonalobdii/id6743419784)

This app helps mechanics streamline vehicle drive cycles by providing live tracking of emissions monitors and diagnostic trouble codes. It offers precise guidance on drive cycle parameters and instant explanations for trouble codes, ensuring accurate diagnostics and faster vehicle readiness for inspection.

**Highlights:** Live drive cycle monitoring, Immediate DTC identification, Real-time monitor completion verification, Precise drive cycle parameter guidance, Professional, easy-to-navigate dashboard, Instant trouble code explanations

**In-app purchases (4)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Diagonal Premium Monthly | $12.99 | per month |
| Diagonal Premium Trial | $12.99 | per month |
| Shop Owner - Monthly | $17.99 | per month |
| Diagonal Premium Yearly | $99.99 | per year |


## Frequently asked questions

### Is TCM Turbo free?

TCM Turbo is free to download, with no in-app purchases.

### Is DiagonalOBDII free?

DiagonalOBDII is free to download, with in-app purchases available.

### Which has better reviews, TCM Turbo or DiagonalOBDII?

TCM Turbo and DiagonalOBDII are both rated 5.0 out of 5 on the App Store, from 1 and 1 ratings respectively.

### Do TCM Turbo or DiagonalOBDII have ads?

Neither TCM Turbo nor DiagonalOBDII shows ads.

### Which is updated more often, TCM Turbo or DiagonalOBDII?

TCM Turbo ships an update every 4 months, and DiagonalOBDII every 2 weeks. Most recently, TCM Turbo was updated on November 1, 2026 and DiagonalOBDII on November 4, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*