DiagonalOBDII vs AiQuest
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
DiagonalOBDII
This app helps mechanics perform vehicle drive cycles more efficiently. It provides real-time monitoring of emissions monitors and diagnostic trouble codes (DTCs), offering clear guidance and instant explanations to ensure vehicles pass inspection quickly and accurately.
- Live drive cycle monitoring
- Immediate diagnostic trouble code (DTC) identification
- Real-time emissions monitor status
- Precise drive cycle parameter guidance
- Professional, easy-to-navigate dashboard
- Instant code explanations
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Diagonal is designed specifically for mechanics who want to simplify and speed up vehicle drive cycles. Instantly track emissions monitors and diagnostic trouble codes (DTCs) live, ensuring accurate diagnostics and rapid vehicle readiness for inspection. Key Features: -Live Drive Cycle Monitoring: Clearly see the real-time status of emissions monitors as they run, complete, or require further action during your drive. -Immediate Diagnostics: Quickly identify and address active trouble codes (DTCs) as they appear, eliminating uncertainty during drive cycles. -Efficiency and Accuracy: Avoid unnecessary repeat drive cycles by verifying real-time monitor completion, ensuring vehicles pass inspection on the first try. -Precise Drive Cycle Guidance: Monitor essential drive cycle parameters such as speed, RPM, engine temperature, and throttle position to meet exact diagnostic requirements. -Professional Dashboard: Access all critical information quickly through a clear, easy-to-navigate interface tailored for automotive professionals. -Instant Code Explanations: Quickly interpret trouble codes with straightforward, mechanic-friendly explanations. Why Mechanics Trust Diagonal: -Saves Valuable Time: Complete diagnostic drive cycles accurately the first time. -Faster Inspections: Immediately identify vehicle readiness to streamline your workflow. -Reduces Diagnostic Uncertainty: Clear, actionable data presented in real-time. -Diagonal empowers professional technicians with the tools to perform diagnostics faster and more efficiently than ever before. Terms of Use: https://www.apple.com/legal/internet-services/itunes/dev/stdeula/ Privacy Policy: https://diagonal-d070c.web.app/privacy.html
AiQuest
This AI assistant runs entirely on your device, offering powerful LLM capabilities without sending your data to the cloud. Experience fast, private AI interactions powered by local processing.
- On-device AI processing
- Privacy-centric design
- High-performance LLM integration
- Local data storage
- Fast response times
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Experience the future of AI that lives on your device—not in the cloud. AIQuest is a high-performance, privacy-centric AI assistant designed to give you the power of advanced Large Language Models (LLMs) like Google’s Gemma, running entirely locally on your iPhone. By leveraging Apple’s Metal GPU via MLX, AIQuest delivers lightning-fast responses while ensuring your sensitive data never leaves your device Thanks karthik juluri
Screenshots
Verdict
DiagonalOBDII and AiQuest both sit at 5.0 stars, but that hides the real split: 100% of AiQuest's written reviews are positive against 0% of DiagonalOBDII's. AiQuest also leads on in-app purchases (none vs 4). On price, rating, ratings volume and update cadence there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
Both are free to download. DiagonalOBDII sells 4 in-app purchases, starting at $12.99 per month. AiQuest asks for nothing beyond the download.
On the App Store both sit at effectively the same score — 5.0 for DiagonalOBDII against 5.0 for AiQuest. Both are backed by a comparable volume of ratings — 1 and 1 respectively. Written reviews are what separate them: 0% of DiagonalOBDII's written reviews are positive against 100% of AiQuest's.
DiagonalOBDII ships an update every 2 weeks, AiQuest every 3 weeks. The most recent releases landed on October 22, 2026 and October 31, 2026 respectively.
| Parameter | DiagonalOBDII | AiQuest |
|---|---|---|
| Price | Free | Free |
| Rating | 5.0 (1 ratings) | 5.0 (1 ratings) |
| Positive reviews | 0.0% of reviews | 100.0% of reviews — better |
| Number of ratings | 1 | 1 |
| Update frequency | Every 2 weeks — better | Every 3 weeks |
| Ads | No | No |
| In-app purchases | Yes | No — better |
| Monetization | Free with in-app purchases | Free — better |
| Devices | iPhone | iPhone, iPad — better |
| Requires iOS | 18.1 | 18.0 — better |
| Further details — not scored | ||
| Size | 21 MB | 31 MB |
| Age rating | 4+ | 4+ |
| Developer | Kyle Louderback | Brahmani Mekala |
Customer experience
DiagonalOBDII
AiQuest
In-app purchases
DiagonalOBDII
- Diagonal Premium Monthly$12.991 Month
- Diagonal Premium Trial1 Month trial$12.991 Month
- Shop Owner - Monthly$17.991 Month
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- Diagonal Premium Yearly$99.991 Year
AiQuest
No in-app purchases









